RE: [PATCH 03/18] vfio/mdev: Simplify driver registration

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> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Wednesday, March 24, 2021 1:55 AM
> 
> This is only done once, we don't need to generate code to initialize a
> structure stored in the ELF .data segment. Fill in the three required
> .driver members directly instead of copying data into them during
> mdev_register_driver().
> 
> Further the to_mdev_driver() function doesn't belong in a public header,
> just inline it into the two places that need it. Finally, we can now
> clearly see that 'drv' derived from dev->driver cannot be NULL, firstly
> because the driver core forbids it, and secondly because NULL won't pass
> through the container_of(). Remove the dead code.
> 
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

> ---
>  Documentation/driver-api/vfio-mediated-device.rst |  5 +----
>  drivers/vfio/mdev/mdev_driver.c                   | 15 +++++++--------
>  drivers/vfio/mdev/vfio_mdev.c                     |  8 ++++++--
>  include/linux/mdev.h                              |  6 +-----
>  4 files changed, 15 insertions(+), 19 deletions(-)
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> b/Documentation/driver-api/vfio-mediated-device.rst
> index c43c1dc3333373..1779b85f014e2f 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -98,13 +98,11 @@ structure to represent a mediated device's driver::
> 
>       /*
>        * struct mdev_driver [2] - Mediated device's driver
> -      * @name: driver name
>        * @probe: called when new device created
>        * @remove: called when device removed
>        * @driver: device driver structure
>        */
>       struct mdev_driver {
> -	     const char *name;
>  	     int  (*probe)  (struct mdev_device *dev);
>  	     void (*remove) (struct mdev_device *dev);
>  	     struct device_driver    driver;
> @@ -115,8 +113,7 @@ to register and unregister itself with the core driver:
> 
>  * Register::
> 
> -    extern int  mdev_register_driver(struct mdev_driver *drv,
> -				   struct module *owner);
> +    extern int  mdev_register_driver(struct mdev_driver *drv);
> 
>  * Unregister::
> 
> diff --git a/drivers/vfio/mdev/mdev_driver.c
> b/drivers/vfio/mdev/mdev_driver.c
> index 44c3ba7e56d923..041699571b7e55 100644
> --- a/drivers/vfio/mdev/mdev_driver.c
> +++ b/drivers/vfio/mdev/mdev_driver.c
> @@ -39,7 +39,8 @@ static void mdev_detach_iommu(struct mdev_device
> *mdev)
> 
>  static int mdev_probe(struct device *dev)
>  {
> -	struct mdev_driver *drv = to_mdev_driver(dev->driver);
> +	struct mdev_driver *drv =
> +		container_of(dev->driver, struct mdev_driver, driver);
>  	struct mdev_device *mdev = to_mdev_device(dev);
>  	int ret;
> 
> @@ -47,7 +48,7 @@ static int mdev_probe(struct device *dev)
>  	if (ret)
>  		return ret;
> 
> -	if (drv && drv->probe) {
> +	if (drv->probe) {
>  		ret = drv->probe(mdev);
>  		if (ret)
>  			mdev_detach_iommu(mdev);
> @@ -58,10 +59,11 @@ static int mdev_probe(struct device *dev)
> 
>  static int mdev_remove(struct device *dev)
>  {
> -	struct mdev_driver *drv = to_mdev_driver(dev->driver);
> +	struct mdev_driver *drv =
> +		container_of(dev->driver, struct mdev_driver, driver);
>  	struct mdev_device *mdev = to_mdev_device(dev);
> 
> -	if (drv && drv->remove)
> +	if (drv->remove)
>  		drv->remove(mdev);
> 
>  	mdev_detach_iommu(mdev);
> @@ -79,16 +81,13 @@ EXPORT_SYMBOL_GPL(mdev_bus_type);
>  /**
>   * mdev_register_driver - register a new MDEV driver
>   * @drv: the driver to register
> - * @owner: module owner of driver to be registered
>   *
>   * Returns a negative value on error, otherwise 0.
>   **/
> -int mdev_register_driver(struct mdev_driver *drv, struct module *owner)
> +int mdev_register_driver(struct mdev_driver *drv)
>  {
>  	/* initialize common driver fields */
> -	drv->driver.name = drv->name;
>  	drv->driver.bus = &mdev_bus_type;
> -	drv->driver.owner = owner;
> 
>  	/* register with core */
>  	return driver_register(&drv->driver);
> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
> index 91b7b8b9eb9cb8..cc9507ed85a181 100644
> --- a/drivers/vfio/mdev/vfio_mdev.c
> +++ b/drivers/vfio/mdev/vfio_mdev.c
> @@ -152,14 +152,18 @@ static void vfio_mdev_remove(struct mdev_device
> *mdev)
>  }
> 
>  static struct mdev_driver vfio_mdev_driver = {
> -	.name	= "vfio_mdev",
> +	.driver = {
> +		.name = "vfio_mdev",
> +		.owner = THIS_MODULE,
> +		.mod_name = KBUILD_MODNAME,
> +	},
>  	.probe	= vfio_mdev_probe,
>  	.remove	= vfio_mdev_remove,
>  };
> 
>  static int __init vfio_mdev_init(void)
>  {
> -	return mdev_register_driver(&vfio_mdev_driver, THIS_MODULE);
> +	return mdev_register_driver(&vfio_mdev_driver);
>  }
> 
>  static void __exit vfio_mdev_exit(void)
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 52f7ea19dd0f56..cb771c712da0f4 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -137,21 +137,17 @@ struct mdev_type_attribute
> mdev_type_attr_##_name =		\
> 
>  /**
>   * struct mdev_driver - Mediated device driver
> - * @name: driver name
>   * @probe: called when new device created
>   * @remove: called when device removed
>   * @driver: device driver structure
>   *
>   **/
>  struct mdev_driver {
> -	const char *name;
>  	int (*probe)(struct mdev_device *dev);
>  	void (*remove)(struct mdev_device *dev);
>  	struct device_driver driver;
>  };
> 
> -#define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
> -
>  static inline void *mdev_get_drvdata(struct mdev_device *mdev)
>  {
>  	return mdev->driver_data;
> @@ -170,7 +166,7 @@ extern struct bus_type mdev_bus_type;
>  int mdev_register_device(struct device *dev, const struct mdev_parent_ops
> *ops);
>  void mdev_unregister_device(struct device *dev);
> 
> -int mdev_register_driver(struct mdev_driver *drv, struct module *owner);
> +int mdev_register_driver(struct mdev_driver *drv);
>  void mdev_unregister_driver(struct mdev_driver *drv);
> 
>  struct device *mdev_parent_dev(struct mdev_device *mdev);
> --
> 2.31.0





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