Re: [PATCH v4 4/5] mikrobus: Add mikroBUS driver

[Vaishnav Achath <vaishnav.a@xxxxxx>]

Hi Ayush,

On 18/03/24 01:07, Ayush Singh wrote:
> DONOTMERGE
>
> this patch depends on Patch 1, 2, 3
>
> mikroBUS driver aims to split the platform aspects of mikroBUS (pinmux,
> SPI/I2C/GPIO controller .etc) from the add-on board information, thus
> requiring one device tree overlay per port and just a single manifest
> describing the add-on board.
>
> The driver exposes a sysfs entry that allows passing mikroBUS manifest of
> add-on board to the driver. The driver then parses this manifest, sets up
> the pins and protocols and allows using the appropriate Linux driver. Here
> is an example:

In v3 series, Krzysztof mentioned that you need to document the ABI, the 
feedback was not considered in the series, see:
https://www.kernel.org/doc/Documentation/ABI/README

Also he mentioned that the mechanism of adding devices from userspace 
needs to be discussed first, that feedback also was not responded to.

These add-on boards are not electrically hot-pluggable and this kind of 
sysfs interface seems to give the idea that you can add an add-on board 
on a running system (which is not recommended due to latchup/other 
electrical failures), I will recommend you discuss the pending feedback 
and discuss on acceptable solutions before spinning future revisions.

> ```
> cat /lib/firmware/mikrobus/AMBIENT-2-CLICK.mnfb > /sys/bus/mikrobus/devices/mikrobus-0/new_device
> ```
>
> Another sysfs entry is exposed that allows removing a previously
> registered mikrobus add-on board:
>
> ```
> echo " " > /sys/bus/mikrobus/devices/mikrobus-0/delete_device
> ```
>
> 100s of mikroBUS addon board manifests can be found in the clickID
> repository.
>
> In the future the driver also aims to support plug and play support
> using 1-wire EEPROM and mikroBUS over greybus.
>
> Link: https://www.mikroe.com/clickid ClickID
>
> Co-developed-by: Vaishnav M A <vaishnav@xxxxxxxxxxxxxxx>
> Signed-off-by: Vaishnav M A <vaishnav@xxxxxxxxxxxxxxx>
> Signed-off-by: Ayush Singh <ayushdevel1325@xxxxxxxxx>
> ---
>   MAINTAINERS                               |   1 +
>   drivers/misc/Kconfig                      |   1 +
>   drivers/misc/Makefile                     |   1 +
>   drivers/misc/mikrobus/Kconfig             |  15 +
>   drivers/misc/mikrobus/Makefile            |   5 +
>   drivers/misc/mikrobus/mikrobus_core.c     | 696 ++++++++++++++++++++++
>   drivers/misc/mikrobus/mikrobus_core.h     | 151 +++++
>   drivers/misc/mikrobus/mikrobus_manifest.c | 503 ++++++++++++++++
>   drivers/misc/mikrobus/mikrobus_manifest.h |  29 +
>   9 files changed, 1402 insertions(+)
>   create mode 100644 drivers/misc/mikrobus/Kconfig
>   create mode 100644 drivers/misc/mikrobus/Makefile
>   create mode 100644 drivers/misc/mikrobus/mikrobus_core.c
>   create mode 100644 drivers/misc/mikrobus/mikrobus_core.h
>   create mode 100644 drivers/misc/mikrobus/mikrobus_manifest.c
>   create mode 100644 drivers/misc/mikrobus/mikrobus_manifest.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 69418a058c6b..83bc5e48bef9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14772,6 +14772,7 @@ M:	Ayush Singh <ayushdevel1325@xxxxxxxxx>
>   M:	Vaishnav M A <vaishnav@xxxxxxxxxxxxxxx>
>   S:	Maintained
>   F:	Documentation/devicetree/bindings/misc/mikrobus-connector.yaml
> +F:	drivers/misc/mikrobus/*
>   
>   MIKROTIK CRS3XX 98DX3236 BOARD SUPPORT
>   M:	Luka Kovacic <luka.kovacic@xxxxxxxxxx>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 4fb291f0bf7c..3d5c36205c6c 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -591,4 +591,5 @@ source "drivers/misc/cardreader/Kconfig"
>   source "drivers/misc/uacce/Kconfig"
>   source "drivers/misc/pvpanic/Kconfig"
>   source "drivers/misc/mchp_pci1xxxx/Kconfig"
> +source "drivers/misc/mikrobus/Kconfig"
>   endmenu
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index ea6ea5bbbc9c..b9ac88055b87 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -68,3 +68,4 @@ obj-$(CONFIG_TMR_INJECT)	+= xilinx_tmr_inject.o
>   obj-$(CONFIG_TPS6594_ESM)	+= tps6594-esm.o
>   obj-$(CONFIG_TPS6594_PFSM)	+= tps6594-pfsm.o
>   obj-$(CONFIG_NSM)		+= nsm.o
> +obj-y				+= mikrobus/
> diff --git a/drivers/misc/mikrobus/Kconfig b/drivers/misc/mikrobus/Kconfig
> new file mode 100644
> index 000000000000..aa57b994dc66
> --- /dev/null
> +++ b/drivers/misc/mikrobus/Kconfig
> @@ -0,0 +1,15 @@
> +menuconfig MIKROBUS
> +	tristate "Module for instantiating devices on mikroBUS ports"
> +	depends on GPIOLIB
> +	help
> +	  This option enables the mikroBUS driver. mikroBUS is an add-on
> +	  board socket standard that offers maximum expandability with
> +	  the smallest number of pins. The mikroBUS driver instantiates
> +	  devices on a mikroBUS port described mikroBUS manifest which is
> +	  passed using a sysfs interface.
> +
> +
> +	  Say Y here to enable support for this driver.
> +
> +	  To compile this code as a module, chose M here: the module
> +	  will be called mikrobus.ko
> diff --git a/drivers/misc/mikrobus/Makefile b/drivers/misc/mikrobus/Makefile
> new file mode 100644
> index 000000000000..0e51c5a7db4b
> --- /dev/null
> +++ b/drivers/misc/mikrobus/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# mikroBUS Core
> +
> +obj-$(CONFIG_MIKROBUS) += mikrobus.o
> +mikrobus-y :=	mikrobus_core.o	mikrobus_manifest.o
> diff --git a/drivers/misc/mikrobus/mikrobus_core.c b/drivers/misc/mikrobus/mikrobus_core.c
> new file mode 100644
> index 000000000000..6aa20cef8e3b
> --- /dev/null
> +++ b/drivers/misc/mikrobus/mikrobus_core.c
> @@ -0,0 +1,696 @@
> +// SPDX-License-Identifier: GPL-2.0:
> +/*
> + * mikroBUS driver for instantiating add-on
> + * board devices with an identifier EEPROM
> + *
> + * Copyright 2020 Vaishnav M A, BeagleBoard.org Foundation.
> + * Copyright 2024 Ayush Singh <ayushdevel1325@xxxxxxxxx>
> + */
> +
> +#define pr_fmt(fmt) "mikrobus:%s: " fmt, __func__
> +
> +#include "linux/gpio/driver.h"
> +#include "linux/gpio/machine.h"
> +#include "linux/gpio/consumer.h"
> +#include "linux/greybus/greybus_manifest.h"
> +#include "linux/i2c.h"
> +#include "linux/irq.h"
> +#include "linux/pinctrl/consumer.h"
> +#include "linux/platform_device.h"
> +#include "linux/spi/spi.h"
> +
> +#include "mikrobus_core.h"
> +#include "mikrobus_manifest.h"
> +
> +static struct class_compat *mikrobus_port_compat_class;
> +
> +static const struct bus_type mikrobus_bus_type = {
> +	.name = "mikrobus",
> +};
> +
> +static int mikrobus_board_register(struct mikrobus_port *port,
> +				   struct addon_board_info *board);
> +static void mikrobus_board_unregister(struct mikrobus_port *port,
> +				      struct addon_board_info *board);
> +
> +/*
> + * mikrobus_pinctrl_select: Select pinctrl state for mikrobus pin
> + *
> + * @port: mikrobus port
> + * @pinctrl_selected: pinctrl state to be selected
> + */
> +static int mikrobus_pinctrl_select(struct mikrobus_port *port,
> +				   const char *pinctrl_selected)
> +{
> +	struct pinctrl_state *state;
> +	int ret;
> +
> +	state = pinctrl_lookup_state(port->pinctrl, pinctrl_selected);
> +	if (IS_ERR(state)) {
> +		return dev_err_probe(&port->dev, PTR_ERR(state),
> +				     "failed to find state %s",
> +				     pinctrl_selected);
> +	}
> +
> +	ret = pinctrl_select_state(port->pinctrl, state);
> +	if (ret) {
> +		return dev_err_probe(&port->dev, ret,
> +				     "failed to select state %s",
> +				     pinctrl_selected);
> +	}
> +	dev_dbg(&port->dev, "setting pinctrl %s", pinctrl_selected);
> +
> +	return 0;
> +}
> +
> +/*
> + * mikrobus_pinctrl_setup: Setup mikrobus pins to either default of gpio
> + *
> + * @port: mikrobus port
> + * @board: mikrobus board or NULL for default state
> + *
> + * returns 0 on success, negative error code on failure
> + */
> +static int mikrobus_pinctrl_setup(struct mikrobus_port *port,
> +				  struct addon_board_info *board)
> +{
> +	int ret;
> +
> +	if (!board || board->pin_state[MIKROBUS_PIN_PWM] == MIKROBUS_STATE_PWM)
> +		ret = mikrobus_pinctrl_select(port, "pwm_default");
> +	else
> +		ret = mikrobus_pinctrl_select(port, "pwm_gpio");
> +	if (ret)
> +		return ret;
> +
> +	if (!board || board->pin_state[MIKROBUS_PIN_RX] == MIKROBUS_STATE_UART)
> +		ret = mikrobus_pinctrl_select(port, "uart_default");
> +	else
> +		ret = mikrobus_pinctrl_select(port, "uart_gpio");
> +	if (ret)
> +		return ret;
> +
> +	if (!board || board->pin_state[MIKROBUS_PIN_SCL] == MIKROBUS_STATE_I2C)
> +		ret = mikrobus_pinctrl_select(port, "i2c_default");
> +	else
> +		ret = mikrobus_pinctrl_select(port, "i2c_gpio");
> +	if (ret)
> +		return ret;
> +
> +	if (!board || board->pin_state[MIKROBUS_PIN_MOSI] == MIKROBUS_STATE_SPI)
> +		ret = mikrobus_pinctrl_select(port, "spi_default");
> +	else
> +		ret = mikrobus_pinctrl_select(port, "spi_gpio");
> +
> +	return ret;
> +}
> +
> +/*
> + * new_device_store: Expose sysfs entry for adding new board
> + *
> + * new_device_store: Allows userspace to add mikroBUS boards that lack 1-wire
> + * EEPROM for board identification by manually passing mikroBUS manifest
> + */
> +static ssize_t new_device_store(struct device *dev,
> +				struct device_attribute *attr, const char *buf,
> +				size_t count)
> +{
> +	struct mikrobus_port *port = to_mikrobus_port(dev);
> +	struct addon_board_info *board;
> +	int ret;
> +
> +	if (port->board)
> +		return dev_err_probe(dev, -EBUSY,
> +				     "already has board registered");
> +
> +	board = devm_kzalloc(&port->dev, sizeof(*board), GFP_KERNEL);
> +	if (!board)
> +		return -ENOMEM;
> +
> +	INIT_LIST_HEAD(&board->manifest_descs);
> +	INIT_LIST_HEAD(&board->devices);
> +
> +	ret = mikrobus_manifest_parse(board, (void *)buf, count);
> +	if (ret < 0) {
> +		ret = dev_err_probe(dev, -EINVAL, "failed to parse manifest");
> +		goto err_free_board;
> +	}
> +
> +	ret = mikrobus_board_register(port, board);
> +	if (ret) {
> +		ret = dev_err_probe(dev, -EINVAL, "failed to register board %s",
> +				    board->name);
> +		goto err_free_board;
> +	}
> +
> +	return count;
> +
> +err_free_board:
> +	devm_kfree(&port->dev, board);
> +	return ret;
> +}
> +static DEVICE_ATTR_WO(new_device);
> +
> +/*
> + * delete_device_store: Expose sysfs entry for deleting board
> + */
> +static ssize_t delete_device_store(struct device *dev,
> +				   struct device_attribute *attr,
> +				   const char *buf, size_t count)
> +{
> +	struct mikrobus_port *port = to_mikrobus_port(dev);
> +
> +	if (!port->board)
> +		return dev_err_probe(dev, -ENODEV,
> +				     "does not have registered boards");
> +
> +	mikrobus_board_unregister(port, port->board);
> +	return count;
> +}
> +static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, 0200, NULL,
> +				  delete_device_store);
> +
> +static struct attribute *mikrobus_port_attrs[] = { &dev_attr_new_device.attr,
> +						   &dev_attr_delete_device.attr,
> +						   NULL };
> +ATTRIBUTE_GROUPS(mikrobus_port);
> +
> +static void mikrobus_port_release(struct device *dev)
> +{
> +}
> +
> +static const struct device_type mikrobus_port_type = {
> +	.groups = mikrobus_port_groups,
> +	.release = mikrobus_port_release,
> +};
> +
> +static int mikrobus_irq_get(struct mikrobus_port *port, int irqno, int irq_type)
> +{
> +	int irq;
> +
> +	if (irqno > port->gpios->ndescs - 1)
> +		return dev_err_probe(&port->dev, -ENODEV,
> +				     "GPIO %d does not exist", irqno);
> +
> +	irq = gpiod_to_irq(port->gpios->desc[irqno]);
> +	if (irq < 0)
> +		return dev_err_probe(&port->dev, -EINVAL,
> +				     "could not get irq %d", irqno);
> +
> +	irq_set_irq_type(irq, irq_type);
> +
> +	return irq;
> +}
> +
> +static int mikrobus_gpio_setup(struct gpio_desc *gpio, int gpio_state)
> +{
> +	switch (gpio_state) {
> +	case MIKROBUS_STATE_INPUT:
> +		return gpiod_direction_input(gpio);
> +	case MIKROBUS_STATE_OUTPUT_HIGH:
> +		return gpiod_direction_output(gpio, 1);
> +	case MIKROBUS_STATE_OUTPUT_LOW:
> +		return gpiod_direction_output(gpio, 0);
> +	case MIKROBUS_STATE_PWM:
> +	case MIKROBUS_STATE_SPI:
> +	case MIKROBUS_STATE_I2C:
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static char *mikrobus_gpio_chip_name_get(struct mikrobus_port *port, int gpio)
> +{
> +	struct gpio_chip *gpiochip;
> +
> +	if (gpio > port->gpios->ndescs - 1)
> +		return NULL;
> +
> +	gpiochip = gpiod_to_chip(port->gpios->desc[gpio]);
> +	return kmemdup(gpiochip->label, strlen(gpiochip->label), GFP_KERNEL);
> +}
> +
> +static int mikrobus_gpio_hwnum_get(struct mikrobus_port *port, int gpio)
> +{
> +	struct gpio_chip *gpiochip;
> +
> +	if (gpio > port->gpios->ndescs - 1)
> +		return -ENODEV;
> +
> +	gpiochip = gpiod_to_chip(port->gpios->desc[gpio]);
> +	return desc_to_gpio(port->gpios->desc[gpio]) - gpiochip->base;
> +}
> +
> +static void mikrobus_board_device_release_all(struct addon_board_info *info)
> +{
> +	struct board_device_info *dev, *next;
> +
> +	list_for_each_entry_safe(dev, next, &info->devices, links) {
> +		list_del(&dev->links);
> +		kfree(dev);
> +	}
> +}
> +
> +static int mikrobus_device_register(struct mikrobus_port *port,
> +				    struct board_device_info *dev,
> +				    char *board_name)
> +{
> +	struct gpiod_lookup_table *lookup;
> +	struct spi_board_info *spi_info;
> +	struct i2c_board_info *i2c_info;
> +	struct platform_device *pdev;
> +	struct fwnode_handle *fwnode;
> +	struct spi_device *spi;
> +	struct i2c_client *i2c;
> +	int i, ret;
> +
> +	dev_info(&port->dev, "registering device : %s", dev->drv_name);
> +
> +	if (dev->gpio_lookup) {
> +		lookup = dev->gpio_lookup;
> +
> +		switch (dev->protocol) {
> +		case GREYBUS_PROTOCOL_SPI:
> +			lookup->dev_id = kasprintf(GFP_KERNEL, "%s.%u",
> +						   dev->drv_name,
> +						   port->chip_select[dev->reg]);
> +			break;
> +		case GREYBUS_PROTOCOL_RAW:
> +			lookup->dev_id = kasprintf(GFP_KERNEL, "%s.%u",
> +						   dev->drv_name, dev->reg);
> +			break;
> +		default:
> +			lookup->dev_id = kmemdup(dev->drv_name,
> +						 strlen(dev->drv_name),
> +						 GFP_KERNEL);
> +		}
> +
> +		dev_info(&port->dev, "adding lookup table : %s",
> +			 lookup->dev_id);
> +
> +		for (i = 0; i < dev->num_gpio_resources; i++) {
> +			lookup->table[i].key = mikrobus_gpio_chip_name_get(
> +				port, lookup->table[i].chip_hwnum);
> +			lookup->table[i].chip_hwnum = mikrobus_gpio_hwnum_get(
> +				port, lookup->table[i].chip_hwnum);
> +		}
> +
> +		gpiod_add_lookup_table(lookup);
> +	}
> +
> +	switch (dev->protocol) {
> +	case GREYBUS_PROTOCOL_SPI:
> +		spi_info =
> +			devm_kzalloc(&port->dev, sizeof(*spi_info), GFP_KERNEL);
> +		strscpy_pad(spi_info->modalias, dev->drv_name,
> +			    sizeof(spi_info->modalias));
> +		if (dev->irq)
> +			spi_info->irq =
> +				mikrobus_irq_get(port, dev->irq, dev->irq_type);
> +		if (dev->properties) {
> +			fwnode = fwnode_create_software_node(dev->properties,
> +							     NULL);
> +			spi_info->swnode = to_software_node(fwnode);
> +		}
> +		spi_info->chip_select = port->chip_select[dev->reg];
> +		spi_info->max_speed_hz = dev->max_speed_hz;
> +		spi_info->mode = dev->mode;
> +
> +		spi = spi_new_device(port->spi_ctrl, spi_info);
> +		devm_kfree(&port->dev, spi_info);
> +		if (!spi)
> +			return dev_err_probe(&port->dev, -ENODEV,
> +					     "failed to register spi device");
> +		dev->dev_client = (void *)spi;
> +		break;
> +	case GREYBUS_PROTOCOL_I2C:
> +		i2c_info =
> +			devm_kzalloc(&port->dev, sizeof(*i2c_info), GFP_KERNEL);
> +		if (!i2c_info)
> +			return -ENOMEM;
> +
> +		strscpy_pad(i2c_info->type, dev->drv_name,
> +			    sizeof(i2c_info->type));
> +		if (dev->irq)
> +			i2c_info->irq =
> +				mikrobus_irq_get(port, dev->irq, dev->irq_type);
> +		if (dev->properties) {
> +			fwnode = fwnode_create_software_node(dev->properties,
> +							     NULL);
> +			i2c_info->swnode = to_software_node(fwnode);
> +		}
> +		i2c_info->addr = dev->reg;
> +
> +		i2c = i2c_new_client_device(port->i2c_adap, i2c_info);
> +		devm_kfree(&port->dev, i2c_info);
> +		if (IS_ERR(dev->dev_client))
> +			return dev_err_probe(&port->dev,
> +					     PTR_ERR(dev->dev_client),
> +					     "failed to register i2c device");
> +		dev->dev_client = (void *)i2c;
> +		break;
> +	case GREYBUS_PROTOCOL_RAW:
> +		pdev = platform_device_alloc(dev->drv_name, 0);
> +		if (!pdev)
> +			return -ENOMEM;
> +
> +		if (dev->properties) {
> +			ret = device_create_managed_software_node(
> +				&pdev->dev, dev->properties, NULL);
> +			if (ret)
> +				return dev_err_probe(
> +					&port->dev, ret,
> +					"failed to create software node");
> +		}
> +		ret = platform_device_add(dev->dev_client);
> +		if (ret)
> +			return dev_err_probe(
> +				&port->dev, ret,
> +				"failed to register platform device");
> +		dev->dev_client = (void *)pdev;
> +		break;
> +	case GREYBUS_PROTOCOL_UART:
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static void mikrobus_device_unregister(struct mikrobus_port *port,
> +				       struct board_device_info *dev,
> +				       char *board_name)
> +{
> +	dev_info(&port->dev, "removing device %s", dev->drv_name);
> +	if (dev->gpio_lookup) {
> +		gpiod_remove_lookup_table(dev->gpio_lookup);
> +		kfree(dev->gpio_lookup->dev_id);
> +		kfree(dev->gpio_lookup);
> +	}
> +
> +	kfree(dev->properties);
> +
> +	switch (dev->protocol) {
> +	case GREYBUS_PROTOCOL_SPI:
> +		spi_unregister_device((struct spi_device *)dev->dev_client);
> +		break;
> +	case GREYBUS_PROTOCOL_I2C:
> +		i2c_unregister_device((struct i2c_client *)dev->dev_client);
> +		break;
> +	case GREYBUS_PROTOCOL_RAW:
> +		platform_device_unregister(
> +			(struct platform_device *)dev->dev_client);
> +		break;
> +	case GREYBUS_PROTOCOL_UART:
> +		break;
> +	}
> +}
> +
> +static int mikrobus_board_register(struct mikrobus_port *port,
> +				   struct addon_board_info *board)
> +{
> +	struct board_device_info *devinfo, *next;
> +	int ret, i;
> +
> +	if (WARN_ON(list_empty(&board->devices)))
> +		return false;
> +
> +	if (port->pinctrl) {
> +		ret = mikrobus_pinctrl_setup(port, board);
> +		if (ret)
> +			dev_err(&port->dev,
> +				"failed to setup pinctrl state [%d]", ret);
> +	}
> +
> +	if (port->gpios) {
> +		for (i = 0; i < port->gpios->ndescs; i++) {
> +			ret = mikrobus_gpio_setup(port->gpios->desc[i],
> +						  board->pin_state[i]);
> +			if (ret)
> +				dev_err(&port->dev,
> +					"failed to setup gpio %d, state %d", i,
> +					board->pin_state[i]);
> +
> +			gpiochip_free_own_desc(port->gpios->desc[i]);
> +		}
> +	}
> +
> +	list_for_each_entry_safe(devinfo, next, &board->devices, links)
> +		mikrobus_device_register(port, devinfo, board->name);
> +
> +	port->board = board;
> +	return 0;
> +}
> +
> +static void mikrobus_board_unregister(struct mikrobus_port *port,
> +				      struct addon_board_info *board)
> +{
> +	struct board_device_info *devinfo, *next;
> +
> +	if (WARN_ON(list_empty(&board->devices)))
> +		return;
> +
> +	list_for_each_entry_safe(devinfo, next, &board->devices, links)
> +		mikrobus_device_unregister(port, devinfo, board->name);
> +
> +	mikrobus_board_device_release_all(board);
> +	devm_kfree(&port->dev, board);
> +	port->board = NULL;
> +}
> +
> +static int mikrobus_port_register(struct mikrobus_port *port)
> +{
> +	int ret;
> +
> +	port->dev.bus = &mikrobus_bus_type;
> +	port->dev.type = &mikrobus_port_type;
> +	dev_set_name(&port->dev, "mikrobus-%d", port->id);
> +
> +	dev_info(&port->dev, "registering port %s", dev_name(&port->dev));
> +
> +	ret = device_register(&port->dev);
> +	if (ret)
> +		return dev_err_probe(&port->dev, ret,
> +				     "port '%d': can't register device (%d)",
> +				     port->id, ret);
> +
> +	ret = class_compat_create_link(mikrobus_port_compat_class, &port->dev,
> +				       port->dev.parent);
> +	if (ret)
> +		dev_warn(&port->dev,
> +			 "failed to create compatibility class link");
> +
> +	return ret;
> +}
> +
> +static void mikrobus_port_delete(struct mikrobus_port *port)
> +{
> +	if (port->board)
> +		return dev_err(
> +			&port->dev,
> +			"attempting to delete port with registered boards, port [%s]",
> +			dev_name(&port->dev));
> +
> +	class_compat_remove_link(mikrobus_port_compat_class, &port->dev,
> +				 port->dev.parent);
> +
> +	devm_pinctrl_put(port->pinctrl);
> +	put_device(&port->spi_ctrl->dev);
> +	gpiod_put_array(port->gpios);
> +	put_device(&port->i2c_adap->dev);
> +
> +	device_unregister(&port->dev);
> +	memset(&port->dev, 0, sizeof(port->dev));
> +}
> +
> +static int mikrobus_port_probe_pinctrl_setup(struct mikrobus_port *port)
> +{
> +	struct device *dev = port->dev.parent;
> +	struct pinctrl_state *state;
> +	int ret;
> +
> +	state = pinctrl_lookup_state(port->pinctrl, PINCTRL_STATE_DEFAULT);
> +	if (IS_ERR(state))
> +		return dev_err_probe(dev, PTR_ERR(state),
> +				     "failed to find state %s",
> +				     PINCTRL_STATE_DEFAULT);
> +
> +	ret = pinctrl_select_state(port->pinctrl, state);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to select state %s",
> +				     PINCTRL_STATE_DEFAULT);
> +
> +	ret = mikrobus_pinctrl_setup(port, NULL);
> +	if (ret)
> +		dev_err(dev, "failed to select pinctrl states [%d]", ret);
> +
> +	return ret;
> +}
> +
> +static int mikrobus_port_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mikrobus_port *port;
> +	struct device_node *np;
> +	int ret;
> +
> +	port = devm_kzalloc(dev, sizeof(*port), GFP_KERNEL);
> +	if (!port)
> +		return -ENOMEM;
> +
> +	port->dev.parent = dev;
> +	port->dev.of_node = pdev->dev.of_node;
> +
> +	/* port id */
> +	port->id = of_alias_get_id(dev->of_node, "mikrobus");
> +	if (port->id) {
> +		ret = dev_err_probe(dev, -EINVAL, "invalid mikrobus id");
> +		goto err_port;
> +	}
> +
> +	/* I2C setup */
> +	np = of_parse_phandle(dev->of_node, "i2c-adapter", 0);
> +	if (!np) {
> +		ret = dev_err_probe(dev, -ENODEV, "cannot parse i2c-adapter");
> +		goto err_port;
> +	}
> +	port->i2c_adap = of_find_i2c_adapter_by_node(np);
> +	of_node_put(np);
> +	if (!port->i2c_adap) {
> +		ret = dev_err_probe(dev, -ENODEV, "cannot find i2c adapter");
> +		goto err_port;
> +	}
> +
> +	/* GPIO setup */
> +	port->gpios = gpiod_get_array(dev, "mikrobus", GPIOD_OUT_LOW);
> +	if (IS_ERR(port->gpios)) {
> +		ret = dev_err_probe(dev, PTR_ERR(port->gpios),
> +				    "failed to get gpio array [%ld]",
> +				    PTR_ERR(port->gpios));
> +		goto free_i2c;
> +	}
> +
> +	/* SPI setup */
> +	np = of_parse_phandle(dev->of_node, "spi-controller", 0);
> +	if (!np) {
> +		ret = dev_err_probe(dev, -ENODEV,
> +				    "cannot parse spi-controller");
> +		goto free_gpio;
> +	}
> +	port->spi_ctrl = of_find_spi_controller_by_node(np);
> +	of_node_put(np);
> +	if (!port->spi_ctrl) {
> +		ret = dev_err_probe(dev, -ENODEV, "cannot find spi controller");
> +		goto free_gpio;
> +	}
> +	ret = device_property_read_u32_array(dev, "spi-cs", port->chip_select,
> +					     MIKROBUS_NUM_CS);
> +	if (ret) {
> +		dev_err(dev, "failed to get spi-cs [%d]", ret);
> +		goto free_spi;
> +	}
> +
> +	/* pinctrl setup */
> +	port->pinctrl = devm_pinctrl_get(dev);
> +	if (IS_ERR(port->pinctrl)) {
> +		ret = dev_err_probe(dev, PTR_ERR(port->pinctrl),
> +				    "failed to get pinctrl [%ld]",
> +				    PTR_ERR(port->pinctrl));
> +		goto free_spi;
> +	}
> +	ret = mikrobus_port_probe_pinctrl_setup(port);
> +	if (ret) {
> +		dev_err(dev, "failed to setup pinctrl [%d]", ret);
> +		goto free_pinctrl;
> +	}
> +
> +	/* TODO: UART */
> +	/* TODO: PWM */
> +
> +	ret = mikrobus_port_register(port);
> +	if (ret) {
> +		dev_err(dev, "port : can't register port [%d]", ret);
> +		goto free_pinctrl;
> +	}
> +
> +	platform_set_drvdata(pdev, port);
> +
> +	return 0;
> +
> +free_pinctrl:
> +	devm_pinctrl_put(port->pinctrl);
> +free_spi:
> +	put_device(&port->spi_ctrl->dev);
> +free_gpio:
> +	gpiod_put_array(port->gpios);
> +free_i2c:
> +	put_device(&port->i2c_adap->dev);
> +err_port:
> +	put_device(&port->dev);
> +	return ret;
> +}
> +
> +static int mikrobus_port_remove(struct platform_device *pdev)
> +{
> +	struct mikrobus_port *port = platform_get_drvdata(pdev);
> +
> +	mikrobus_port_delete(port);
> +	return 0;
> +}
> +
> +static const struct of_device_id mikrobus_port_of_match[] = {
> +	{ .compatible = "mikrobus-connector" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, mikrobus_port_of_match);
> +
> +static struct platform_driver mikrobus_port_driver = {
> +	.probe = mikrobus_port_probe,
> +	.remove = mikrobus_port_remove,
> +	.driver = {
> +		.name = "mikrobus",
> +		.of_match_table = mikrobus_port_of_match,
> +	},
> +};
> +
> +static int mikrobus_init(void)
> +{
> +	int ret;
> +
> +	ret = bus_register(&mikrobus_bus_type);
> +	if (ret) {
> +		pr_err("bus_register failed (%d)", ret);
> +		return ret;
> +	}
> +
> +	mikrobus_port_compat_class = class_compat_register("mikrobus-port");
> +	if (!mikrobus_port_compat_class) {
> +		ret = -ENOMEM;
> +		pr_err("class_compat register failed (%d)", ret);
> +		goto class_err;
> +	}
> +
> +	ret = platform_driver_register(&mikrobus_port_driver);
> +	if (ret)
> +		pr_err("driver register failed [%d]", ret);
> +
> +	return ret;
> +
> +class_err:
> +	bus_unregister(&mikrobus_bus_type);
> +	return ret;
> +}
> +subsys_initcall(mikrobus_init);
> +
> +static void mikrobus_exit(void)
> +{
> +	platform_driver_unregister(&mikrobus_port_driver);
> +	bus_unregister(&mikrobus_bus_type);
> +	class_compat_unregister(mikrobus_port_compat_class);
> +}
> +module_exit(mikrobus_exit);
> +
> +MODULE_AUTHOR("Vaishnav M A <vaishnav@xxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Ayush Singh <ayushdevel1325@xxxxxxxxxxxxxxx>");

This e-mail is different from your Signed-off-by:/ MAINTAINERS entry, 
was this intentional?

Thanks and Regards,
Vaishnav

> +MODULE_DESCRIPTION("mikroBUS main module");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/misc/mikrobus/mikrobus_core.h b/drivers/misc/mikrobus/mikrobus_core.h
> new file mode 100644
> index 000000000000..1d41ee32ca94
> --- /dev/null
> +++ b/drivers/misc/mikrobus/mikrobus_core.h
> @@ -0,0 +1,151 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * mikroBUS Driver for instantiating add-on board devices
> + *
> + * Copyright 2020 Vaishnav M A, BeagleBoard.org Foundation.
> + * Copyright 2024 Ayush Singh <ayushdevel1325@xxxxxxxxx>
> + */
> +
> +#ifndef __MIKROBUS_H
> +#define __MIKROBUS_H
> +
> +#include "linux/device.h"
> +
> +#define MIKROBUS_VERSION_MAJOR 0x00
> +#define MIKROBUS_VERSION_MINOR 0x03
> +
> +#define MIKROBUS_NUM_PINCTRL_STATE 4
> +#define MIKROBUS_NUM_CS 2
> +
> +#define MIKROBUS_PINCTRL_PWM 0
> +#define MIKROBUS_PINCTRL_UART 1
> +#define MIKROBUS_PINCTRL_I2C 2
> +#define MIKROBUS_PINCTRL_SPI 3
> +
> +enum mikrobus_property_type {
> +	MIKROBUS_PROPERTY_TYPE_MIKROBUS = 0x00,
> +	MIKROBUS_PROPERTY_TYPE_PROPERTY,
> +	MIKROBUS_PROPERTY_TYPE_GPIO,
> +	MIKROBUS_PROPERTY_TYPE_U8,
> +	MIKROBUS_PROPERTY_TYPE_U16,
> +	MIKROBUS_PROPERTY_TYPE_U32,
> +	MIKROBUS_PROPERTY_TYPE_U64,
> +};
> +
> +enum mikrobus_pin {
> +	MIKROBUS_PIN_PWM = 0x00,
> +	MIKROBUS_PIN_INT,
> +	MIKROBUS_PIN_RX,
> +	MIKROBUS_PIN_TX,
> +	MIKROBUS_PIN_SCL,
> +	MIKROBUS_PIN_SDA,
> +	MIKROBUS_PIN_MOSI,
> +	MIKROBUS_PIN_MISO,
> +	MIKROBUS_PIN_SCK,
> +	MIKROBUS_PIN_CS,
> +	MIKROBUS_PIN_RST,
> +	MIKROBUS_PIN_AN,
> +	MIKROBUS_PORT_PIN_COUNT,
> +};
> +
> +enum mikrobus_pin_state {
> +	MIKROBUS_STATE_INPUT = 0x01,
> +	MIKROBUS_STATE_OUTPUT_HIGH,
> +	MIKROBUS_STATE_OUTPUT_LOW,
> +	MIKROBUS_STATE_PWM,
> +	MIKROBUS_STATE_SPI,
> +	MIKROBUS_STATE_I2C,
> +	MIKROBUS_STATE_UART,
> +};
> +
> +/*
> + * board_device_info describes a single device on a mikrobus add-on
> + * board, an add-on board can present one or more device to the host
> + *
> + * @gpio_lookup: used to provide the GPIO lookup table for
> + * passing the named GPIOs to device drivers.
> + * @properties: used to provide the property_entry to pass named
> + * properties to device drivers, applicable only when driver uses
> + * device_property_read_* calls to fetch the properties.
> + * @num_gpio_resources: number of named gpio resources for the device,
> + * used mainly for gpiod_lookup_table memory allocation.
> + * @num_properties: number of custom properties for the device,
> + * used mainly for property_entry memory allocation.
> + * @protocol: used to know the type of the device and it should
> + * contain one of the values defined under 'enum greybus_class_type'
> + * under linux/greybus/greybus_manifest.h
> + * @reg: I2C address for the device, for devices on the SPI bus
> + * this field is the chip select address relative to the mikrobus
> + * port:0->device chip select connected to CS pin on mikroBUS port
> + *	1->device chip select connected to RST Pin on mikroBUS port
> + * @mode: SPI mode
> + * @max_speed_hz: SPI max speed(Hz)
> + * @drv_name: device_id to match with the driver
> + * @irq_type: type of IRQ trigger , match with defines in linux/interrupt.h
> + * @irq: irq number relative to the mikrobus port should contain one of the
> + * values defined under 'enum mikrobus_pin'
> + * @id: device id starting from 1
> + */
> +struct board_device_info {
> +	struct gpiod_lookup_table *gpio_lookup;
> +	struct property_entry *properties;
> +	struct list_head links;
> +	unsigned short num_gpio_resources;
> +	unsigned short num_properties;
> +	unsigned short protocol;
> +	unsigned short reg;
> +	unsigned int mode;
> +	void *dev_client;
> +	u32 max_speed_hz;
> +	char *drv_name;
> +	int irq_type;
> +	int irq;
> +	int id;
> +};
> +
> +/*
> + * addon_board_info describes a mikrobus add-on device the add-on
> + * board, an add-on board can present one or more device to the host
> + *
> + * @manifest_descs: list of manifest descriptors
> + * @devices: list of devices on the board
> + * @pin_state: the state of each pin on the mikrobus port required
> + * for the add-on board should contain one of the values defined under
> + * 'enum mikrobus_pin_state' restrictions are as per mikrobus standard
> + * specifications.
> + * @name: add-on board name
> + */
> +struct addon_board_info {
> +	struct list_head manifest_descs;
> +	struct list_head devices;
> +	u8 pin_state[MIKROBUS_PORT_PIN_COUNT];
> +	char *name;
> +};
> +
> +/*
> + * mikrobus_port describes the peripherals mapped to a mikrobus port.
> + *
> + * @chip_select: chip select number mapped to the SPI CS pin on the
> + * mikrobus port and the RST pin on the mikrobus port
> + * @board: pointer to the attached add-on board.
> + * @spi_ctrl: SPI controller attached to the mikrobus port.
> + * @i2c_adap: I2C adapter attached to the mikrobus port.
> + * @gpios: GPIOs attached to the mikrobus port.
> + * @pinctrl: pinctrl attached to the mikrobus port.
> + * @dev: device structure for the mikrobus port.
> + * @id: port id starting from 1
> + */
> +struct mikrobus_port {
> +	u32 chip_select[MIKROBUS_NUM_CS];
> +	struct addon_board_info *board;
> +	struct spi_controller *spi_ctrl;
> +	struct i2c_adapter *i2c_adap;
> +	struct gpio_descs *gpios;
> +	struct pinctrl *pinctrl;
> +	struct device dev;
> +	int id;
> +};
> +
> +#define to_mikrobus_port(d) container_of(d, struct mikrobus_port, dev)
> +
> +#endif /* __MIKROBUS_H */
> diff --git a/drivers/misc/mikrobus/mikrobus_manifest.c b/drivers/misc/mikrobus/mikrobus_manifest.c
> new file mode 100644
> index 000000000000..5f30620277be
> --- /dev/null
> +++ b/drivers/misc/mikrobus/mikrobus_manifest.c
> @@ -0,0 +1,503 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * mikroBUS manifest parsing, an
> + * extension to Greybus Manifest Parsing
> + * under drivers/greybus/manifest.c
> + *
> + * Copyright 2014-2015 Google Inc.
> + * Copyright 2014-2015 Linaro Ltd.
> + * Copyright 2024 Ayush Singh <ayushdevel1325@xxxxxxxxx>
> + */
> +
> +#define pr_fmt(fmt) "mikrobus_manifest:%s: " fmt, __func__
> +
> +#include "linux/gpio/machine.h"
> +#include "linux/greybus/greybus_manifest.h"
> +#include "linux/property.h"
> +#include "mikrobus_manifest.h"
> +
> +struct manifest_desc {
> +	struct list_head links;
> +	size_t size;
> +	void *data;
> +	enum greybus_descriptor_type type;
> +};
> +
> +static void manifest_descriptor_release_all(struct addon_board_info *board)
> +{
> +	struct manifest_desc *descriptor, *next;
> +
> +	list_for_each_entry_safe(descriptor, next, &board->manifest_descs,
> +				 links) {
> +		list_del(&descriptor->links);
> +		kfree(descriptor);
> +	}
> +}
> +
> +static int board_descriptor_add(struct addon_board_info *board,
> +				struct greybus_descriptor *desc, size_t size)
> +{
> +	struct greybus_descriptor_header *desc_header = &desc->header;
> +	struct manifest_desc *descriptor;
> +	size_t desc_size, expected_size;
> +
> +	if (size < sizeof(*desc_header)) {
> +		pr_err("short descriptor (%zu < %zu)", size,
> +		       sizeof(*desc_header));
> +		return -EINVAL;
> +	}
> +
> +	desc_size = le16_to_cpu(desc_header->size);
> +	if (desc_size > size) {
> +		pr_err("incorrect descriptor size (%zu != %zu)", size,
> +		       desc_size);
> +		return -EINVAL;
> +	}
> +
> +	expected_size = sizeof(*desc_header);
> +	switch (desc_header->type) {
> +	case GREYBUS_TYPE_STRING:
> +		expected_size += sizeof(struct greybus_descriptor_string);
> +		expected_size += desc->string.length;
> +		expected_size = ALIGN(expected_size, 4);
> +		break;
> +	case GREYBUS_TYPE_PROPERTY:
> +		expected_size += sizeof(struct greybus_descriptor_property);
> +		expected_size += desc->property.length;
> +		expected_size = ALIGN(expected_size, 4);
> +		break;
> +	case GREYBUS_TYPE_DEVICE:
> +		expected_size += sizeof(struct greybus_descriptor_device);
> +		break;
> +	case GREYBUS_TYPE_MIKROBUS:
> +		expected_size += sizeof(struct greybus_descriptor_mikrobus);
> +		break;
> +	case GREYBUS_TYPE_INTERFACE:
> +		expected_size += sizeof(struct greybus_descriptor_interface);
> +		break;
> +	case GREYBUS_TYPE_CPORT:
> +		expected_size += sizeof(struct greybus_descriptor_cport);
> +		break;
> +	case GREYBUS_TYPE_BUNDLE:
> +		expected_size += sizeof(struct greybus_descriptor_bundle);
> +		break;
> +	case GREYBUS_TYPE_INVALID:
> +	default:
> +		pr_err("invalid descriptor type %d", desc_header->type);
> +		return -EINVAL;
> +	}
> +
> +	descriptor = kzalloc(sizeof(*descriptor), GFP_KERNEL);
> +	if (!descriptor)
> +		return -ENOMEM;
> +
> +	descriptor->size = desc_size;
> +	descriptor->data = (char *)desc + sizeof(*desc_header);
> +	descriptor->type = desc_header->type;
> +	list_add_tail(&descriptor->links, &board->manifest_descs);
> +
> +	return desc_size;
> +}
> +
> +static char *mikrobus_string_get(struct addon_board_info *board, u8 string_id)
> +{
> +	struct greybus_descriptor_string *desc_string;
> +	struct manifest_desc *descriptor;
> +	bool found = false;
> +	char *string;
> +
> +	if (!string_id)
> +		return NULL;
> +
> +	list_for_each_entry(descriptor, &board->manifest_descs, links) {
> +		if (descriptor->type != GREYBUS_TYPE_STRING)
> +			continue;
> +
> +		desc_string = descriptor->data;
> +		if (desc_string->id == string_id) {
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	if (!found)
> +		return ERR_PTR(-ENOENT);
> +
> +	string = kmemdup(&desc_string->string, desc_string->length + 1,
> +			 GFP_KERNEL);
> +	if (!string)
> +		return ERR_PTR(-ENOMEM);
> +
> +	string[desc_string->length] = '\0';
> +
> +	return string;
> +}
> +
> +static void mikrobus_state_get(struct addon_board_info *board)
> +{
> +	struct greybus_descriptor_mikrobus *mikrobus;
> +	struct greybus_descriptor_interface *interface;
> +	struct manifest_desc *descriptor;
> +	bool found = false;
> +	size_t i;
> +
> +	list_for_each_entry(descriptor, &board->manifest_descs, links) {
> +		if (descriptor->type == GREYBUS_TYPE_MIKROBUS) {
> +			mikrobus = descriptor->data;
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	if (!found) {
> +		pr_err("mikrobus descriptor not found");
> +		return;
> +	}
> +
> +	for (i = 0; i < MIKROBUS_PORT_PIN_COUNT; i++)
> +		board->pin_state[i] = mikrobus->pin_state[i];
> +
> +	found = false;
> +	list_for_each_entry(descriptor, &board->manifest_descs, links) {
> +		if (descriptor->type == GREYBUS_TYPE_INTERFACE) {
> +			interface = descriptor->data;
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	if (!found) {
> +		pr_err("interface descriptor not found");
> +		return;
> +	}
> +
> +	board->name = mikrobus_string_get(board, interface->product_stringid);
> +}
> +
> +static struct property_entry *
> +mikrobus_property_entry_get(struct addon_board_info *board, u8 *prop_link,
> +			    int num_properties)
> +{
> +	struct greybus_descriptor_property *desc_property;
> +	struct manifest_desc *descriptor;
> +	struct property_entry *properties;
> +	bool found = false;
> +	char *prop_name;
> +	int i, ret;
> +	u64 *val_u64;
> +	u32 *val_u32;
> +	u16 *val_u16;
> +	u8 *val_u8;
> +
> +	properties = kcalloc(num_properties, sizeof(*properties), GFP_KERNEL);
> +	if (!properties)
> +		return ERR_PTR(-ENOMEM);
> +
> +	for (i = 0; i < num_properties; i++) {
> +		list_for_each_entry(descriptor, &board->manifest_descs, links) {
> +			if (descriptor->type != GREYBUS_TYPE_PROPERTY)
> +				continue;
> +
> +			desc_property = descriptor->data;
> +			if (desc_property->id == prop_link[i]) {
> +				found = true;
> +				break;
> +			}
> +		}
> +
> +		if (!found) {
> +			ret = -ENOENT;
> +			goto early_exit;
> +		}
> +
> +		prop_name = mikrobus_string_get(
> +			board, desc_property->propname_stringid);
> +		if (!prop_name) {
> +			ret = -ENOENT;
> +			goto early_exit;
> +		}
> +
> +		switch (desc_property->type) {
> +		case MIKROBUS_PROPERTY_TYPE_U8:
> +			val_u8 = kmemdup(&desc_property->value,
> +					 (desc_property->length) * sizeof(u8),
> +					 GFP_KERNEL);
> +			if (desc_property->length == 1)
> +				properties[i] =
> +					PROPERTY_ENTRY_U8(prop_name, *val_u8);
> +			else
> +				properties[i] = PROPERTY_ENTRY_U8_ARRAY_LEN(
> +					prop_name, (void *)desc_property->value,
> +					desc_property->length);
> +			break;
> +		case MIKROBUS_PROPERTY_TYPE_U16:
> +			val_u16 = kmemdup(&desc_property->value,
> +					  (desc_property->length) * sizeof(u16),
> +					  GFP_KERNEL);
> +			if (desc_property->length == 1)
> +				properties[i] =
> +					PROPERTY_ENTRY_U16(prop_name, *val_u16);
> +			else
> +				properties[i] = PROPERTY_ENTRY_U16_ARRAY_LEN(
> +					prop_name, (void *)desc_property->value,
> +					desc_property->length);
> +			break;
> +		case MIKROBUS_PROPERTY_TYPE_U32:
> +			val_u32 = kmemdup(&desc_property->value,
> +					  (desc_property->length) * sizeof(u32),
> +					  GFP_KERNEL);
> +			if (desc_property->length == 1)
> +				properties[i] =
> +					PROPERTY_ENTRY_U32(prop_name, *val_u32);
> +			else
> +				properties[i] = PROPERTY_ENTRY_U32_ARRAY_LEN(
> +					prop_name, (void *)desc_property->value,
> +					desc_property->length);
> +			break;
> +		case MIKROBUS_PROPERTY_TYPE_U64:
> +			val_u64 = kmemdup(&desc_property->value,
> +					  (desc_property->length) * sizeof(u64),
> +					  GFP_KERNEL);
> +			if (desc_property->length == 1)
> +				properties[i] =
> +					PROPERTY_ENTRY_U64(prop_name, *val_u64);
> +			else
> +				properties[i] = PROPERTY_ENTRY_U64_ARRAY_LEN(
> +					prop_name, (void *)desc_property->value,
> +					desc_property->length);
> +			break;
> +		default:
> +			ret = -EINVAL;
> +			goto early_exit;
> +		}
> +	}
> +	return properties;
> +
> +early_exit:
> +	kfree(properties);
> +	return ERR_PTR(ret);
> +}
> +
> +static u8 *mikrobus_property_link_get(struct addon_board_info *board,
> +				      u8 prop_id,
> +				      struct board_device_info *board_dev,
> +				      u8 prop_type)
> +{
> +	struct greybus_descriptor_property *desc_property;
> +	struct manifest_desc *descriptor;
> +	bool found = false;
> +	u8 *val_u8;
> +
> +	if (!prop_id)
> +		return NULL;
> +
> +	list_for_each_entry(descriptor, &board->manifest_descs, links) {
> +		if (descriptor->type != GREYBUS_TYPE_PROPERTY)
> +			continue;
> +
> +		desc_property = descriptor->data;
> +		if (desc_property->id == prop_id &&
> +		    desc_property->type == prop_type) {
> +			found = true;
> +			break;
> +		}
> +	}
> +
> +	if (!found)
> +		return ERR_PTR(-ENOENT);
> +
> +	val_u8 = kmemdup(&desc_property->value, desc_property->length,
> +			 GFP_KERNEL);
> +	if (prop_type == MIKROBUS_PROPERTY_TYPE_GPIO)
> +		board_dev->num_gpio_resources = desc_property->length;
> +	else if (prop_type == MIKROBUS_PROPERTY_TYPE_PROPERTY)
> +		board_dev->num_properties = desc_property->length;
> +
> +	return val_u8;
> +}
> +
> +static int
> +mikrobus_manifest_attach_device(struct addon_board_info *board,
> +				struct greybus_descriptor_device *dev_desc)
> +{
> +	struct greybus_descriptor_property *desc_property;
> +	u8 *gpio_desc_link, *prop_link, *gpioval;
> +	struct board_device_info *board_dev;
> +	struct gpiod_lookup_table *lookup;
> +	struct manifest_desc *descriptor;
> +	int ret, i;
> +
> +	board_dev = kzalloc(sizeof(*board_dev), GFP_KERNEL);
> +	if (!board_dev)
> +		return -ENOMEM;
> +
> +	board_dev->id = dev_desc->id;
> +	board_dev->drv_name =
> +		mikrobus_string_get(board, dev_desc->driver_stringid);
> +	if (!board_dev->drv_name) {
> +		ret = -ENOENT;
> +		goto err_free_board_dev;
> +	}
> +
> +	board_dev->protocol = dev_desc->protocol;
> +	board_dev->reg = dev_desc->reg;
> +	board_dev->irq = dev_desc->irq;
> +	board_dev->irq_type = dev_desc->irq_type;
> +	board_dev->max_speed_hz = le32_to_cpu(dev_desc->max_speed_hz);
> +	board_dev->mode = dev_desc->mode;
> +	pr_info("parsed device %d, driver=%s", board_dev->id,
> +		board_dev->drv_name);
> +
> +	if (dev_desc->prop_link > 0) {
> +		prop_link = mikrobus_property_link_get(
> +			board, dev_desc->prop_link, board_dev,
> +			MIKROBUS_PROPERTY_TYPE_PROPERTY);
> +		if (!prop_link) {
> +			ret = -ENOENT;
> +			goto err_free_board_dev;
> +		}
> +
> +		pr_info("device %d, number of properties=%d", board_dev->id,
> +			board_dev->num_properties);
> +		board_dev->properties = mikrobus_property_entry_get(
> +			board, prop_link, board_dev->num_properties);
> +	}
> +
> +	if (dev_desc->gpio_link > 0) {
> +		gpio_desc_link = mikrobus_property_link_get(
> +			board, dev_desc->gpio_link, board_dev,
> +			MIKROBUS_PROPERTY_TYPE_GPIO);
> +		if (!gpio_desc_link) {
> +			ret = -ENOENT;
> +			goto err_free_board_dev;
> +		}
> +
> +		pr_info("device %d, number of gpio resource=%d", board_dev->id,
> +			board_dev->num_gpio_resources);
> +		lookup = kzalloc(struct_size(lookup, table,
> +					     board_dev->num_gpio_resources),
> +				 GFP_KERNEL);
> +		if (!lookup) {
> +			ret = -ENOMEM;
> +			goto err_free_board_dev;
> +		}
> +
> +		for (i = 0; i < board_dev->num_gpio_resources; i++) {
> +			list_for_each_entry(descriptor, &board->manifest_descs,
> +					    links) {
> +				if (descriptor->type != GREYBUS_TYPE_PROPERTY)
> +					continue;
> +
> +				desc_property = descriptor->data;
> +				if (desc_property->id == gpio_desc_link[i]) {
> +					gpioval = desc_property->value;
> +					lookup->table[i].chip_hwnum =
> +						gpioval[0];
> +					lookup->table[i].flags = gpioval[1];
> +					lookup->table[i]
> +						.con_id = mikrobus_string_get(
> +						board,
> +						desc_property
> +							->propname_stringid);
> +					break;
> +				}
> +			}
> +		}
> +		board_dev->gpio_lookup = lookup;
> +	}
> +
> +	list_add_tail(&board_dev->links, &board->devices);
> +	return 0;
> +
> +err_free_board_dev:
> +	kfree(board_dev);
> +	return ret;
> +}
> +
> +static int mikrobus_manifest_parse_devices(struct addon_board_info *board)
> +{
> +	struct greybus_descriptor_device *desc_device;
> +	struct manifest_desc *desc, *next;
> +	int ret, devcount = 0;
> +
> +	list_for_each_entry_safe(desc, next, &board->manifest_descs, links) {
> +		if (desc->type != GREYBUS_TYPE_DEVICE)
> +			continue;
> +
> +		desc_device = desc->data;
> +		ret = mikrobus_manifest_attach_device(board, desc_device);
> +		devcount++;
> +	}
> +
> +	return devcount;
> +}
> +
> +static size_t mikrobus_manifest_header_validate(void *data, size_t size)
> +{
> +	struct greybus_manifest_header *header = data;
> +	u16 manifest_size = le16_to_cpu(header->size);
> +
> +	if (manifest_size < sizeof(*header)) {
> +		pr_err("short manifest (%zu < %zu)", size, sizeof(*header));
> +		return -EINVAL;
> +	}
> +
> +	if (header->version_major > MIKROBUS_VERSION_MAJOR) {
> +		pr_err("manifest version too new (%u.%u > %u.%u)",
> +		       header->version_major, header->version_minor,
> +		       MIKROBUS_VERSION_MAJOR, MIKROBUS_VERSION_MINOR);
> +		return -EINVAL;
> +	}
> +
> +	return manifest_size;
> +}
> +
> +int mikrobus_manifest_parse(struct addon_board_info *board, void *data,
> +			    size_t size)
> +{
> +	struct greybus_manifest_header *header;
> +	struct greybus_manifest *manifest;
> +	struct greybus_descriptor *desc;
> +	int dev_count, desc_size, ret;
> +	u16 manifest_size;
> +
> +	if (size < sizeof(*header)) {
> +		pr_err("short manifest (%zu < %zu)", size, sizeof(*header));
> +		return -EINVAL;
> +	}
> +
> +	ret = mikrobus_manifest_header_validate(data, size);
> +	if (ret < 0) {
> +		pr_err("invalid manifest header: %u", manifest_size);
> +		return ret;
> +	}
> +
> +	manifest = data;
> +	manifest_size = ret;
> +
> +	if (manifest_size != size) {
> +		pr_err("invalid manifest size(%zu < %u)", size, manifest_size);
> +		return -EINVAL;
> +	}
> +
> +	desc = manifest->descriptors;
> +	size -= sizeof(*header);
> +	while (size) {
> +		desc_size = board_descriptor_add(board, desc, size);
> +		if (desc_size < 0) {
> +			pr_err("invalid manifest descriptor, size: %u",
> +			       desc_size);
> +			return -EINVAL;
> +		}
> +
> +		desc = (void *)desc + desc_size;
> +		size -= desc_size;
> +	}
> +
> +	mikrobus_state_get(board);
> +	dev_count = mikrobus_manifest_parse_devices(board);
> +	pr_info("%s manifest parsed with %d devices", board->name, dev_count);
> +	manifest_descriptor_release_all(board);
> +
> +	return dev_count;
> +}
> diff --git a/drivers/misc/mikrobus/mikrobus_manifest.h b/drivers/misc/mikrobus/mikrobus_manifest.h
> new file mode 100644
> index 000000000000..39ae53a25fc4
> --- /dev/null
> +++ b/drivers/misc/mikrobus/mikrobus_manifest.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * mikroBUS manifest definition
> + * extension to Greybus Manifest Definition
> + *
> + * Copyright 2014-2015 Google Inc.
> + * Copyright 2014-2015 Linaro Ltd.
> + *
> + * Released under the GPLv2 and BSD licenses.
> + */
> +
> +#ifndef __MIKROBUS_MANIFEST_H
> +#define __MIKROBUS_MANIFEST_H
> +
> +#include "mikrobus_core.h"
> +
> +/*
> + * mikrobus_manifest_header - parse mikroBUS manifest
> + *
> + * @info: addon board info structure to populate with parsed information
> + * @data: pointer to the manifest blob
> + * @size: size of the manifest blob
> + *
> + * returns: number of devices on success, negative error code on failure
> + */
> +int mikrobus_manifest_parse(struct addon_board_info *info, void *data,
> +			    size_t size);
> +
> +#endif /* __MIKROBUS_MANIFEST_H */
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