Re: [net-next v2 1/9] Implementation of Virtual Bus

[Leon Romanovsky <leonro@mellanox.com>]

On Tue, Apr 21, 2020 at 01:02:27AM -0700, Jeff Kirsher wrote:
> From: Dave Ertman <david.m.ertman@intel.com>
>
> 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 registering
> virtbus_devices and virtbus_drivers and provide matching
> between them and probing of the registered drivers.
>
> 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@intel.com>
> Signed-off-by: Kiran Patil <kiran.patil@intel.com>
> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> ---
>  Documentation/driver-api/virtual_bus.rst |  62 +++++
>  drivers/bus/Kconfig                      |  10 +
>  drivers/bus/Makefile                     |   2 +
>  drivers/bus/virtual_bus.c                | 279 +++++++++++++++++++++++
>  include/linux/mod_devicetable.h          |   8 +
>  include/linux/virtual_bus.h              |  53 +++++
>  scripts/mod/devicetable-offsets.c        |   3 +
>  scripts/mod/file2alias.c                 |   7 +
>  8 files changed, 424 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
>
> diff --git a/Documentation/driver-api/virtual_bus.rst b/Documentation/driver-api/virtual_bus.rst
> new file mode 100644
> index 000000000000..a79db0e9231e
> --- /dev/null
> +++ b/Documentation/driver-api/virtual_bus.rst
> @@ -0,0 +1,62 @@
> +===============================
> +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 support the minimal device functionality.  Devices will
> +accept a name, and then, when added to the virtual bus, an automatically
> +generated index is concatenated onto it for the virtbus_device->name.
> +
> +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_register_driver and unregister with virtbus_unregister_driver.
> +
> +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)
> +
> +Virtbus device IDs are always in "<name>.<instance>" format.  Instances are
> +automatically selected through an ida_simple_get so are positive integers.
> +Name is 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.
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 6d4e4497b59b..00553c78510c 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -203,4 +203,14 @@ config DA8XX_MSTPRI
>  source "drivers/bus/fsl-mc/Kconfig"
>  source "drivers/bus/mhi/Kconfig"
>
> +config VIRTUAL_BUS
> +       tristate "Software based Virtual Bus"
> +       help
> +         Provides a software bus for virtbus_devices to be added to it
> +         and virtbus_drivers to be registered on it.  It matches driver
> +         and device based on id and calls the driver's probe routine.
> +         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.
> +
>  endmenu
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index 05f32cd694a4..d30828a4768c 100644
> --- a/drivers/bus/Makefile
> +++ b/drivers/bus/Makefile
> @@ -37,3 +37,5 @@ obj-$(CONFIG_DA8XX_MSTPRI)	+= da8xx-mstpri.o
>
>  # MHI
>  obj-$(CONFIG_MHI_BUS)		+= mhi/
> +
> +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..f5e66d110385
> --- /dev/null
> +++ b/drivers/bus/virtual_bus.c
> @@ -0,0 +1,279 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * virtual_bus.c - lightweight software based bus for virtual devices
> + *
> + * Copyright (c) 2019-2020 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("Virtual Bus");
> +MODULE_AUTHOR("David Ertman <david.m.ertman@intel.com>");
> +MODULE_AUTHOR("Kiran Patil <kiran.patil@intel.com>");
> +
> +static DEFINE_IDA(virtbus_dev_ida);
> +
> +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))
> +			return id;
> +		id++;
> +	}
> +	return NULL;
> +}
> +
> +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);
> +
> +	return virtbus_match_id(vdrv->id_table, vdev) != NULL;
> +}
> +
> +static int virtbus_probe(struct device *dev)
> +{
> +	return dev->driver->probe(dev);
> +}
> +
> +static int virtbus_remove(struct device *dev)
> +{
> +	return dev->driver->remove(dev);
> +}
> +
> +static void virtbus_shutdown(struct device *dev)
> +{
> +	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;

The common practice is to write it differently.
static int virtbus_resume(struct device *dev)
{
	if (!dev->driver->resume)
		return 0;

	return dev->driver->resume(dev);
}

and you are not consistent in this patch, sometimes you write
these functions in your format, sometimes in my format.

Thanks