Re: [RFC PATCH 1/3] eeprom: Add a simple EEPROM framework

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On Thu, Feb 19, 2015 at 11:08 AM, Srinivas Kandagatla
<srinivas.kandagatla@xxxxxxxxxx> wrote:
> From: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
>
> Up until now, EEPROM drivers were stored in drivers/misc, where they all had to
> duplicate pretty much the same code to register a sysfs file, allow in-kernel
> users to access the content of the devices they were driving, etc.
>
> This was also a problem as far as other in-kernel users were involved, since
> the solutions used were pretty much different from on driver to another, there
> was a rather big abstraction leak.
>
> This introduction of this framework aims at solving this. It also introduces DT
> representation for consumer devices to go get the data they require (MAC
> Addresses, SoC/Revision ID, part numbers, and so on) from the EEPROMs.
>
> Having regmap interface to this framework would give much better
> abstraction for eeproms on different buses.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> [srinivas.kandagatla: Moved to regmap based and cleanedup apis]
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> ---
>  .../devicetree/bindings/eeprom/eeprom.txt          |  48 ++++
>  drivers/Kconfig                                    |   2 +
>  drivers/Makefile                                   |   1 +
>  drivers/eeprom/Kconfig                             |  19 ++
>  drivers/eeprom/Makefile                            |   9 +
>  drivers/eeprom/core.c                              | 290 +++++++++++++++++++++
>  include/linux/eeprom-consumer.h                    |  73 ++++++
>  include/linux/eeprom-provider.h                    |  51 ++++

Who is going to be the maintainer for this?

>  8 files changed, 493 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/eeprom/eeprom.txt
>  create mode 100644 drivers/eeprom/Kconfig
>  create mode 100644 drivers/eeprom/Makefile
>  create mode 100644 drivers/eeprom/core.c
>  create mode 100644 include/linux/eeprom-consumer.h
>  create mode 100644 include/linux/eeprom-provider.h
>
> diff --git a/Documentation/devicetree/bindings/eeprom/eeprom.txt b/Documentation/devicetree/bindings/eeprom/eeprom.txt
> new file mode 100644
> index 0000000..9ec1ec2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/eeprom/eeprom.txt

Please make bindings a separate patch.

> @@ -0,0 +1,48 @@
> += EEPROM Data Device Tree Bindings =
> +
> +This binding is intended to represent the location of hardware
> +configuration data stored in EEPROMs.
> +
> +On a significant proportion of boards, the manufacturer has stored
> +some data on an EEPROM-like device, for the OS to be able to retrieve
> +these information and act upon it. Obviously, the OS has to know
> +about where to retrieve these data from, and where they are stored on
> +the storage device.
> +
> +This document is here to document this.
> +
> += Data providers =
> +
> +Required properties:
> +#eeprom-cells: Number of cells in an eeprom specifier; The common
> +               case is 2.

We already have eeproms in DTs, it would be nice to be able to support
them with this framework as well.

> +
> +For example:
> +
> +       at24: eeprom@42 {
> +               #eeprom-cells = <2>;
> +       };
> +
> += Data consumers =
> +
> +Required properties:
> +
> +eeproms: List of phandle and data cell specifier triplet, one triplet
> +        for each data cell the device might be interested in. The
> +        triplet consists of the phandle to the eeprom provider, then
> +        the offset in byte within that storage device, and the length
> +        in byte of the data we care about.

The problem with this is it assumes you know who the consumer is and
that it is a DT node. For example, how would you describe a serial
number?

Rob

> +
> +Optional properties:
> +
> +eeprom-names: List of data cell name strings sorted in the same order
> +             as the resets property. Consumers drivers will use
> +             eeprom-names to differentiate between multiple cells,
> +             and hence being able to know what these cells are for.
> +
> +For example:
> +
> +       device {
> +               eeproms = <&at24 14 42>;
> +               eeprom-names = "soc-rev-id";
> +       };
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index c70d6e4..d7afc82 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -184,4 +184,6 @@ source "drivers/thunderbolt/Kconfig"
>
>  source "drivers/android/Kconfig"
>
> +source "drivers/eeprom/Kconfig"
> +
>  endmenu
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 527a6da..57eb5b0 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -165,3 +165,4 @@ obj-$(CONFIG_RAS)           += ras/
>  obj-$(CONFIG_THUNDERBOLT)      += thunderbolt/
>  obj-$(CONFIG_CORESIGHT)                += coresight/
>  obj-$(CONFIG_ANDROID)          += android/
> +obj-$(CONFIG_EEPROM)           += eeprom/
> diff --git a/drivers/eeprom/Kconfig b/drivers/eeprom/Kconfig
> new file mode 100644
> index 0000000..2c5452a
> --- /dev/null
> +++ b/drivers/eeprom/Kconfig
> @@ -0,0 +1,19 @@
> +menuconfig EEPROM
> +       bool "EEPROM Support"
> +       depends on OF
> +       help
> +         Support for EEPROM alike devices.
> +
> +         This framework is designed to provide a generic interface to EEPROM
> +         from both the Linux Kernel and the userspace.
> +
> +         If unsure, say no.
> +
> +if EEPROM
> +
> +config EEPROM_DEBUG
> +       bool "EEPROM debug support"
> +       help
> +         Say yes here to enable debugging support.
> +
> +endif
> diff --git a/drivers/eeprom/Makefile b/drivers/eeprom/Makefile
> new file mode 100644
> index 0000000..e130079
> --- /dev/null
> +++ b/drivers/eeprom/Makefile
> @@ -0,0 +1,9 @@
> +#
> +# Makefile for eeprom drivers.
> +#
> +
> +ccflags-$(CONFIG_EEPROM_DEBUG) += -DDEBUG
> +
> +obj-$(CONFIG_EEPROM)           += core.o
> +
> +# Devices
> diff --git a/drivers/eeprom/core.c b/drivers/eeprom/core.c
> new file mode 100644
> index 0000000..bc877a6
> --- /dev/null
> +++ b/drivers/eeprom/core.c
> @@ -0,0 +1,290 @@
> +/*
> + * EEPROM framework core.
> + *
> + * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> + * Copyright (C) 2013 Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2.  This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/eeprom-provider.h>
> +#include <linux/eeprom-consumer.h>
> +#include <linux/export.h>
> +#include <linux/fs.h>
> +#include <linux/idr.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +struct eeprom_cell {
> +       struct eeprom_device *eeprom;
> +       loff_t offset;
> +       size_t count;
> +};
> +
> +static DEFINE_MUTEX(eeprom_list_mutex);
> +static LIST_HEAD(eeprom_list);
> +static DEFINE_IDA(eeprom_ida);
> +
> +static ssize_t bin_attr_eeprom_read_write(struct kobject *kobj,
> +                                   char *buf, loff_t offset,
> +                                   size_t count, bool read)
> +{
> +       struct device *dev = container_of(kobj, struct device, kobj);
> +       struct eeprom_device *eeprom = container_of(dev, struct eeprom_device,
> +                                                   edev);
> +       int rc;
> +
> +       if (offset > eeprom->size)
> +               return 0;
> +
> +       if (offset + count > eeprom->size)
> +               count = eeprom->size - offset;
> +
> +       if (read)
> +               rc = regmap_bulk_read(eeprom->regmap, offset,
> +                                     buf, count/eeprom->stride);
> +       else
> +               rc = regmap_bulk_write(eeprom->regmap, offset,
> +                                      buf, count/eeprom->stride);
> +
> +       if (IS_ERR_VALUE(rc))
> +               return 0;
> +
> +       return count;
> +}
> +
> +static ssize_t bin_attr_eeprom_read(struct file *filp, struct kobject *kobj,
> +                                   struct bin_attribute *attr,
> +                                   char *buf, loff_t offset, size_t count)
> +{
> +       return bin_attr_eeprom_read_write(kobj, buf, offset, count, true);
> +}
> +
> +static ssize_t bin_attr_eeprom_write(struct file *filp, struct kobject *kobj,
> +                                    struct bin_attribute *attr,
> +                                    char *buf, loff_t offset, size_t count)
> +{
> +       return bin_attr_eeprom_read_write(kobj, buf, offset, count, false);
> +}
> +
> +static struct bin_attribute bin_attr_eeprom = {
> +       .attr   = {
> +               .name   = "eeprom",
> +               .mode   = 0660,
> +       },
> +       .read   = bin_attr_eeprom_read,
> +       .write  = bin_attr_eeprom_write,
> +};
> +
> +static struct bin_attribute *eeprom_bin_attributes[] = {
> +       &bin_attr_eeprom,
> +       NULL,
> +};
> +
> +static const struct attribute_group eeprom_bin_group = {
> +       .bin_attrs      = eeprom_bin_attributes,
> +};
> +
> +static const struct attribute_group *eeprom_dev_groups[] = {
> +       &eeprom_bin_group,
> +       NULL,
> +};
> +
> +static struct class eeprom_class = {
> +       .name           = "eeprom",
> +       .dev_groups     = eeprom_dev_groups,
> +};
> +
> +int eeprom_register(struct eeprom_device *eeprom)
> +{
> +       int rval;
> +
> +       if (!eeprom->regmap || !eeprom->size) {
> +               dev_err(eeprom->dev, "Regmap not found\n");
> +               return -EINVAL;
> +       }
> +
> +       eeprom->id = ida_simple_get(&eeprom_ida, 0, 0, GFP_KERNEL);
> +       if (eeprom->id < 0)
> +               return eeprom->id;
> +
> +       eeprom->edev.class = &eeprom_class;
> +       eeprom->edev.parent = eeprom->dev;
> +       eeprom->edev.of_node = eeprom->dev ? eeprom->dev->of_node : NULL;
> +       dev_set_name(&eeprom->edev, "eeprom%d", eeprom->id);
> +
> +       device_initialize(&eeprom->edev);
> +
> +       dev_dbg(&eeprom->edev, "Registering eeprom device %s\n",
> +               dev_name(&eeprom->edev));
> +
> +       rval = device_add(&eeprom->edev);
> +       if (rval)
> +               return rval;
> +
> +       mutex_lock(&eeprom_list_mutex);
> +       list_add(&eeprom->list, &eeprom_list);
> +       mutex_unlock(&eeprom_list_mutex);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL(eeprom_register);
> +
> +int eeprom_unregister(struct eeprom_device *eeprom)
> +{
> +       device_del(&eeprom->edev);
> +
> +       mutex_lock(&eeprom_list_mutex);
> +       list_del(&eeprom->list);
> +       mutex_unlock(&eeprom_list_mutex);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL(eeprom_unregister);
> +
> +static struct eeprom_cell *__eeprom_cell_get(struct device_node *node,
> +                                            int index)
> +{
> +       struct of_phandle_args args;
> +       struct eeprom_cell *cell;
> +       struct eeprom_device *e, *eeprom = NULL;
> +       int ret;
> +
> +       ret = of_parse_phandle_with_args(node, "eeproms",
> +                                        "#eeprom-cells", index, &args);
> +       if (ret)
> +               return ERR_PTR(ret);
> +
> +       if (args.args_count != 2)
> +               return ERR_PTR(-EINVAL);
> +
> +       mutex_lock(&eeprom_list_mutex);
> +
> +       list_for_each_entry(e, &eeprom_list, list) {
> +               if (args.np == e->edev.of_node) {
> +                       eeprom = e;
> +                       break;
> +               }
> +       }
> +       mutex_unlock(&eeprom_list_mutex);
> +
> +       if (!eeprom)
> +               return ERR_PTR(-EPROBE_DEFER);
> +
> +       cell = kzalloc(sizeof(*cell), GFP_KERNEL);
> +       if (!cell)
> +               return ERR_PTR(-ENOMEM);
> +
> +       cell->eeprom = eeprom;
> +       cell->offset = args.args[0];
> +       cell->count = args.args[1];
> +
> +       return cell;
> +}
> +
> +static struct eeprom_cell *__eeprom_cell_get_byname(struct device_node *node,
> +                                                   const char *id)
> +{
> +       int index = 0;
> +
> +       if (id)
> +               index = of_property_match_string(node,
> +                                                "eeprom-names",
> +                                                id);
> +       return __eeprom_cell_get(node, index);
> +
> +}
> +
> +struct eeprom_cell *eeprom_cell_get(struct device *dev, int index)
> +{
> +       if (!dev)
> +               return ERR_PTR(-EINVAL);
> +
> +       /* First, attempt to retrieve the cell through the DT */
> +       if (dev->of_node)
> +               return __eeprom_cell_get(dev->of_node, index);
> +
> +       /* We don't support anything else yet */
> +       return ERR_PTR(-ENODEV);
> +}
> +EXPORT_SYMBOL(eeprom_cell_get);
> +
> +struct eeprom_cell *eeprom_cell_get_byname(struct device *dev, const char *id)
> +{
> +       if (!dev)
> +               return ERR_PTR(-EINVAL);
> +
> +       if (id && dev->of_node)
> +               return __eeprom_cell_get_byname(dev->of_node, id);
> +
> +       /* We don't support anything else yet */
> +       return ERR_PTR(-ENODEV);
> +}
> +EXPORT_SYMBOL(eeprom_cell_get_byname);
> +
> +void eeprom_cell_put(struct eeprom_cell *cell)
> +{
> +       kfree(cell);
> +}
> +EXPORT_SYMBOL(eeprom_cell_put);
> +
> +char *eeprom_cell_read(struct eeprom_cell *cell, ssize_t *len)
> +{
> +       struct eeprom_device *eeprom = cell->eeprom;
> +       char *buf;
> +       int rc;
> +
> +       if (!eeprom || !eeprom->regmap)
> +               return ERR_PTR(-EINVAL);
> +
> +       buf = kzalloc(cell->count, GFP_KERNEL);
> +       if (!buf)
> +               return ERR_PTR(-ENOMEM);
> +
> +       rc = regmap_bulk_read(eeprom->regmap, cell->offset,
> +                             buf, cell->count/eeprom->stride);
> +       if (IS_ERR_VALUE(rc)) {
> +               kfree(buf);
> +               return ERR_PTR(rc);
> +       }
> +
> +       *len = cell->count;
> +
> +       return buf;
> +}
> +EXPORT_SYMBOL(eeprom_cell_read);
> +
> +int eeprom_cell_write(struct eeprom_cell *cell, const char *buf, ssize_t len)
> +{
> +       struct eeprom_device *eeprom = cell->eeprom;
> +
> +       if (!eeprom || !eeprom->regmap)
> +               return -EINVAL;
> +
> +       return regmap_bulk_write(eeprom->regmap, cell->offset,
> +                                buf, cell->count/eeprom->stride);
> +}
> +EXPORT_SYMBOL(eeprom_cell_write);
> +
> +static int eeprom_init(void)
> +{
> +       return class_register(&eeprom_class);
> +}
> +
> +static void eeprom_exit(void)
> +{
> +       class_unregister(&eeprom_class);
> +}
> +
> +subsys_initcall(eeprom_init);
> +module_exit(eeprom_exit);
> +
> +MODULE_AUTHOR("Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx");
> +MODULE_DESCRIPTION("EEPROM Driver Core");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/eeprom-consumer.h b/include/linux/eeprom-consumer.h
> new file mode 100644
> index 0000000..706ae9d
> --- /dev/null
> +++ b/include/linux/eeprom-consumer.h
> @@ -0,0 +1,73 @@
> +/*
> + * EEPROM framework consumer.
> + *
> + * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> + * Copyright (C) 2013 Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2.  This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#ifndef _LINUX_EEPROM_CONSUMER_H
> +#define _LINUX_EEPROM_CONSUMER_H
> +
> +struct eeprom_cell;
> +
> +/**
> + * eeprom_cell_get(): Get eeprom cell of device form a given index.
> + *
> + * @dev: Device that will be interacted with
> + * @index: Index of the eeprom cell.
> + *
> + * The return value will be an ERR_PTR() on error or a valid pointer
> + * to a struct eeprom_cell.  The eeprom_cell will be freed by the
> + * eeprom_cell_put().
> + */
> +struct eeprom_cell *eeprom_cell_get(struct device *dev, int index);
> +
> +/**
> + * eeprom_cell_get(): Get eeprom cell of device form a given name.
> + *
> + * @dev: Device that will be interacted with
> + * @name: Name of the eeprom cell.
> + *
> + * The return value will be an ERR_PTR() on error or a valid pointer
> + * to a struct eeprom_cell.  The eeprom_cell will be freed by the
> + * eeprom_cell_put().
> + */
> +struct eeprom_cell *eeprom_cell_get_byname(struct device *dev,
> +                                          const char *name);
> +
> +/**
> + * eeprom_cell_put(): Release previously allocated eeprom cell.
> + *
> + * @cell: Previously allocated eeprom cell by eeprom_cell_get()
> + * or eeprom_cell_get_byname().
> + */
> +void eeprom_cell_put(struct eeprom_cell *cell);
> +
> +/**
> + * eeprom_cell_read(): Read a given eeprom cell
> + *
> + * @cell: eeprom cell to be read.
> + * @len: pointer to length of cell which will be populated on successful read.
> + *
> + * The return value will be an ERR_PTR() on error or a valid pointer
> + * to a char * bufffer.  The buffer should be freed by the consumer with a
> + * kfree().
> + */
> +char *eeprom_cell_read(struct eeprom_cell *cell, ssize_t *len);
> +
> +/**
> + * eeprom_cell_write(): Write to a given eeprom cell
> + *
> + * @cell: eeprom cell to be written.
> + * @buf: Buffer to be written.
> + * @len: length of buffer to be written to eeprom cell.
> + *
> + * The return value will be an non zero on error or a zero on successful write.
> + */
> +int eeprom_cell_write(struct eeprom_cell *cell, const char *buf, ssize_t len);
> +
> +#endif  /* ifndef _LINUX_EEPROM_CONSUMER_H */
> diff --git a/include/linux/eeprom-provider.h b/include/linux/eeprom-provider.h
> new file mode 100644
> index 0000000..3943c2f
> --- /dev/null
> +++ b/include/linux/eeprom-provider.h
> @@ -0,0 +1,51 @@
> +/*
> + * EEPROM framework provider.
> + *
> + * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> + * Copyright (C) 2013 Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> + *
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2.  This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#ifndef _LINUX_EEPROM_PROVIDER_H
> +#define _LINUX_EEPROM_PROVIDER_H
> +
> +#include <linux/device.h>
> +#include <linux/regmap.h>
> +#include <linux/list.h>
> +
> +struct eeprom_device {
> +       struct regmap           *regmap;
> +       int                     stride;
> +       size_t                  size;
> +       struct device           *dev;
> +
> +       /* Internal to framework */
> +       struct device           edev;
> +       int                     id;
> +       struct list_head        list;
> +};
> +
> +/**
> + * eeprom_register(): Register a eeprom device for given eeprom.
> + * Also creates an binary entry in /sys/class/eeprom/eeprom[id]/eeprom
> + *
> + * @eeprom: eeprom device that needs to be created
> + *
> + * The return value will be an error code on error or a zero on success.
> + * The eeprom_device and sysfs entery will be freed by the eeprom_unregister().
> + */
> +int eeprom_register(struct eeprom_device *eeprom);
> +
> +/**
> + * eeprom_unregister(): Unregister previously registered eeprom device
> + *
> + * @eeprom: Pointer to previously registered eeprom device.
> + *
> + * The return value will be an non zero on error or a zero on success.
> + */
> +int eeprom_unregister(struct eeprom_device *eeprom);
> +
> +#endif  /* ifndef _LINUX_EEPROM_PROVIDER_H */
> --
> 1.9.1
>
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