On Fri, Nov 15, 2019 at 02:33:55PM -0800, Jeff Kirsher wrote:
> From: Dave Ertman <david.m.ertman@xxxxxxxxx>
>
> This is the initial implementation of the Virtual Bus,
> virtbus_device and virtbus_driver. The virtual bus is
> a software based bus intended to support lightweight
> devices and drivers and provide matching between them
> and probing of the registered drivers.
>
> The primary purpose of the virual bus is to provide
> matching services and to pass the data pointer
> contained in the virtbus_device to the virtbus_driver
> during its probe call. This will allow two separate
> kernel objects to match up and start communication.
>
> The bus will support probe/remove shutdown and
> suspend/resume callbacks.
>
> Kconfig and Makefile alterations are included
>
> Signed-off-by: Dave Ertman <david.m.ertman@xxxxxxxxx>
> Signed-off-by: Kiran Patil <kiran.patil@xxxxxxxxx>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
> ---
> v2: Cleaned up the virtual bus interface based on feedback from Greg KH
> and provided a test driver and test virtual bus device as an example
> of how to implement the virtual bus.
>
> Documentation/driver-api/virtual_bus.rst | 76 ++++
> drivers/bus/Kconfig | 14 +
> drivers/bus/Makefile | 1 +
> drivers/bus/virtual_bus.c | 326 ++++++++++++++++++
> include/linux/virtual_bus.h | 55 +++
> .../virtual_bus/virtual_bus_dev/Makefile | 7 +
> .../virtual_bus_dev/virtual_bus_dev.c | 67 ++++
> .../virtual_bus/virtual_bus_drv/Makefile | 7 +
> .../virtual_bus_drv/virtual_bus_drv.c | 101 ++++++
> 9 files changed, 654 insertions(+)
> create mode 100644 Documentation/driver-api/virtual_bus.rst
> create mode 100644 drivers/bus/virtual_bus.c
> create mode 100644 include/linux/virtual_bus.h
> create mode 100644 tools/testing/selftests/virtual_bus/virtual_bus_dev/Makefile
> create mode 100644 tools/testing/selftests/virtual_bus/virtual_bus_dev/virtual_bus_dev.c
> create mode 100644 tools/testing/selftests/virtual_bus/virtual_bus_drv/Makefile
> create mode 100644 tools/testing/selftests/virtual_bus/virtual_bus_drv/virtual_bus_drv.c
>
> diff --git a/Documentation/driver-api/virtual_bus.rst b/Documentation/driver-api/virtual_bus.rst
> new file mode 100644
> index 000000000000..970e06267284
> --- /dev/null
> +++ b/Documentation/driver-api/virtual_bus.rst
> @@ -0,0 +1,76 @@
> +===============================
> +Virtual Bus Devices and Drivers
> +===============================
> +
> +See <linux/virtual_bus.h> for the models for virtbus_device and virtbus_driver.
> +This bus is meant to be a lightweight software based bus to attach generic
> +devices and drivers to so that a chunk of data can be passed between them.
> +
> +One use case example is an rdma driver needing to connect with several
> +different types of PCI LAN devices to be able to request resources from
> +them (queue sets). Each LAN driver that supports rdma will register a
> +virtbus_device on the virtual bus for each physical function. The rdma
> +driver will register as a virtbus_driver on the virtual bus to be
> +matched up with multiple virtbus_devices and receive a pointer to a
> +struct containing the callbacks that the PCI LAN drivers support for
> +registering with them.
> +
> +Sections in this document:
> + Virtbus devices
> + Virtbus drivers
> + Device Enumeration
> + Device naming and driver binding
> + Virtual Bus API entry points
> +
> +Virtbus devices
> +~~~~~~~~~~~~~~~
> +Virtbus_devices are lightweight objects that support the minimal device
> +functionality. Devices will accept a name, and then an automatically
> +generated index is concatenated onto it for the virtbus_device->name.
> +
> +The memory backing the "void *data" element of the virtbus_device is
> +expected to be allocated and freed outside the context of the bus
> +operations. This memory is also expected to remain viable for the
> +duration of the time that the virtbus_device is registered to the
> +virtual bus. (e.g. from before the virtbus_dev_register until after
> +the paired virtbus_dev_unregister).
> +
> +The provided API for virtbus_dev_alloc is an efficient way of allocating
> +the memory for the virtbus_device (except for the data element) and
> +automatically freeing it when the device is removed from the bus.
> +
> +Virtbus drivers
> +~~~~~~~~~~~~~~~
> +Virtbus drivers register with the virtual bus to be matched with virtbus
> +devices. They expect to be registered with a probe and remove callback,
> +and also support shutdown, suspend, and resume callbacks. They otherwise
> +follow the standard driver behavior of having discovery and enumeration
> +handled in the bus infrastructure.
> +
> +Virtbus drivers register themselves with the API entry point virtbus_drv_reg
> +and unregister with virtbus_drv_unreg.
> +
> +Device Enumeration
> +~~~~~~~~~~~~~~~~~~
> +Enumeration is handled automatically by the bus infrastructure via the
> +ida_simple methods.
> +
> +Device naming and driver binding
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +The virtbus_device.dev.name is the canonical name for the device. It is
> +built from two other parts:
> +
> + - virtbus_device.name (also used for matching).
> + - virtbus_device.id (generated automatically from ida_simple calls)
> +
> +This allows for multiple virtbus_devices with the same name, which will all
> +be matched to the same virtbus_driver. Driver binding is performed by the
> +driver core, invoking driver probe() after finding a match between device and driver.
> +
> +Virtual Bus API entry points
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +struct virtbus_device *virtbus_dev_alloc(const char *name, void *data)
> +int virtbus_dev_register(struct virtbus_device *vdev)
> +void virtbus_dev_unregister(struct virtbus_device *vdev)
> +int virtbus_drv_register(struct virtbus_driver *vdrv, struct module *owner)
> +void virtbus_drv_unregister(struct virtbus_driver *vdrv)
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 6b331061d34b..30cef35b0c30 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -193,4 +193,18 @@ config DA8XX_MSTPRI
>
> source "drivers/bus/fsl-mc/Kconfig"
>
> +config VIRTUAL_BUS
> + tristate "lightweight Virtual Bus"
> + depends on PM
> + help
> + Provides a lightweight bus for virtbus_devices to be added to it
> + and virtbus_drivers to be registered on it. Will create a match
> + between the driver and device, then call the driver's probe with
> + the virtbus_device's struct (including a pointer for data).
> + One example is the irdma driver needing to connect with various
> + PCI LAN drivers to request resources (queues) to be able to perform
> + its function. The data in the virtbus_device created by the
> + PCI LAN driver is a set of ops (function pointers) for the irdma
> + driver to use to register and communicate with the PCI LAN driver.
> +
> endmenu
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index 16b43d3468c6..0b0ba53cbe5b 100644
> --- a/drivers/bus/Makefile
> +++ b/drivers/bus/Makefile
> @@ -33,3 +33,4 @@ obj-$(CONFIG_UNIPHIER_SYSTEM_BUS) += uniphier-system-bus.o
> obj-$(CONFIG_VEXPRESS_CONFIG) += vexpress-config.o
>
> obj-$(CONFIG_DA8XX_MSTPRI) += da8xx-mstpri.o
> +obj-$(CONFIG_VIRTUAL_BUS) += virtual_bus.o
> diff --git a/drivers/bus/virtual_bus.c b/drivers/bus/virtual_bus.c
> new file mode 100644
> index 000000000000..c6eab1658391
> --- /dev/null
> +++ b/drivers/bus/virtual_bus.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * virtual_bus.c - lightweight software based bus for virtual devices
> + *
> + * Copyright (c) 2019-20 Intel Corporation
> + *
> + * Please see Documentation/driver-api/virtual_bus.rst for
> + * more information
> + */
> +
> +#include <linux/string.h>
> +#include <linux/virtual_bus.h>
> +#include <linux/of_irq.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/pm_domain.h>
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Lightweight Virtual Bus");
> +MODULE_AUTHOR("David Ertman <david.m.ertman@xxxxxxxxx>");
> +MODULE_AUTHOR("Kiran Patil <kiran.patil@xxxxxxxxx>");
> +
> +static DEFINE_IDA(virtbus_dev_ida);
Do you ever clean up this when unloaded? I didn't see that happening
but I might have missed it.
> +
> +static const
> +struct virtbus_dev_id *virtbus_match_id(const struct virtbus_dev_id *id,
> + struct virtbus_device *vdev)
> +{
> + while (id->name[0]) {
> + if (!strcmp(vdev->name, id->name)) {
> + vdev->dev_id = id;
Why are you changing/setting the id?
> + return id;
> + }
> + id++;
> + }
> + return NULL;
> +}
> +
> +#define to_virtbus_dev(x) (container_of((x), struct virtbus_device, dev))
> +#define to_virtbus_drv(x) (container_of((x), struct virtbus_driver, \
> + driver))
> +
> +/**
> + * virtbus_match - bind virtbus device to virtbus driver
> + * @dev: device
> + * @drv: driver
> + *
> + * Virtbus device IDs are always in "<name>.<instance>" format.
> + * Instances are automatically selected through an ida_simple_get so
> + * are positive integers. Names are taken from the device name field.
> + * Driver IDs are simple <name>. Need to extract the name from the
> + * Virtual Device compare to name of the driver.
> + */
> +static int virtbus_match(struct device *dev, struct device_driver *drv)
> +{
> + struct virtbus_driver *vdrv = to_virtbus_drv(drv);
> + struct virtbus_device *vdev = to_virtbus_dev(dev);
> +
> + if (vdrv->id_table)
> + return virtbus_match_id(vdrv->id_table, vdev) != NULL;
> +
> + return !strcmp(vdev->name, drv->name);
> +}
> +
> +/**
> + * virtbus_probe - call probe of the virtbus_drv
> + * @dev: device struct
> + */
> +static int virtbus_probe(struct device *dev)
> +{
> + if (dev->driver->probe)
> + return dev->driver->probe(dev);
> +
> + return 0;
> +}
> +
> +static int virtbus_remove(struct device *dev)
> +{
> + if (dev->driver->remove)
> + return dev->driver->remove(dev);
> +
> + return 0;
> +}
> +
> +static void virtbus_shutdown(struct device *dev)
> +{
> + if (dev->driver->shutdown)
> + dev->driver->shutdown(dev);
> +}
> +
> +static int virtbus_suspend(struct device *dev, pm_message_t state)
> +{
> + if (dev->driver->suspend)
> + return dev->driver->suspend(dev, state);
> +
> + return 0;
> +}
> +
> +static int virtbus_resume(struct device *dev)
> +{
> + if (dev->driver->resume)
> + return dev->driver->resume(dev);
> +
> + return 0;
> +}
> +
> +struct bus_type virtual_bus_type = {
> + .name = "virtbus",
> + .match = virtbus_match,
> + .probe = virtbus_probe,
> + .remove = virtbus_remove,
> + .shutdown = virtbus_shutdown,
> + .suspend = virtbus_suspend,
> + .resume = virtbus_resume,
> +};
> +
> +/**
> + * virtbus_dev_register - add a virtual bus device
> + * @vdev: virtual bus device to add
> + */
> +int virtbus_dev_register(struct virtbus_device *vdev)
> +{
> + int ret;
> +
> + if (!vdev)
> + return -EINVAL;
> +
> + device_initialize(&vdev->dev);
> +
> + vdev->dev.bus = &virtual_bus_type;
> + /* All device IDs are automatically allocated */
> + ret = ida_simple_get(&virtbus_dev_ida, 0, 0, GFP_KERNEL);
> + if (ret < 0)
> + return ret;
> +
> + vdev->id = ret;
> + dev_set_name(&vdev->dev, "%s.%d", vdev->name, vdev->id);
> +
> + dev_dbg(&vdev->dev, "Registering VirtBus device '%s'\n",
> + dev_name(&vdev->dev));
> +
> + ret = device_add(&vdev->dev);
> + if (!ret)
> + return ret;
This logic has tripped me up multiple times, it's an anti-pattern.
Please do:
if (ret)
goto device_add_error;
return 0;
device_add_error:
...
> +
> + /* Error adding virtual device */
> + device_del(&vdev->dev);
> + ida_simple_remove(&virtbus_dev_ida, vdev->id);
> + vdev->id = VIRTBUS_DEVID_NONE;
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(virtbus_dev_register);
> +
> +/**
> + * virtbus_dev_unregister - remove a virtual bus device
> + * vdev: virtual bus device we are removing
> + */
> +void virtbus_dev_unregister(struct virtbus_device *vdev)
> +{
> + if (!IS_ERR_OR_NULL(vdev)) {
> + device_del(&vdev->dev);
> +
> + ida_simple_remove(&virtbus_dev_ida, vdev->id);
> + vdev->id = VIRTBUS_DEVID_NONE;
Why set the id? What will care/check this?
> + }
> +}
> +EXPORT_SYMBOL_GPL(virtbus_dev_unregister);
> +
> +struct virtbus_object {
> + struct virtbus_device vdev;
> + char name[];
> +};
Why not use the name in the device structure?
thanks,
greg k-h
