Re: [PATCH v3 7/7] platform: Add platform_find_device_by_driver() helper

[Robin Murphy <robin.murphy@arm.com>]

On 23/07/2019 23:18, Suzuki K Poulose wrote:
> Provide a helper to lookup platform devices by matching device
> driver in order to avoid drivers trying to use platform bus
> internals.

FWIW, this whole drm_match_add idiom really looks like it deserves 
factoring out into an of_platform_populate-style helper, but I guess 
aligning those subtle little differences is a non-trivial challenge.

[and I am well aware of just how much of a big messy can of worms DRM 
device probing is in general]

> Cc: Eric Anholt <eric@anholt.net>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Heiko Stübner" <heiko@sntech.de>
> Cc: Inki Dae <inki.dae@samsung.com>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Sandy Huang <hjc@rock-chips.com>
> Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
> Tested-by: Heiko Stuebner <heiko@sntech.de>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>   drivers/base/platform.c                     | 14 ++++++++++++++
>   drivers/gpu/drm/exynos/exynos_drm_drv.c     |  9 +++------
>   drivers/gpu/drm/mcde/mcde_drv.c             |  3 +--
>   drivers/gpu/drm/rockchip/rockchip_drm_drv.c |  3 +--
>   drivers/gpu/drm/vc4/vc4_drv.c               |  3 +--
>   include/linux/platform_device.h             |  3 +++
>   6 files changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 506a0175a5a7..a174ce5ea17c 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1197,6 +1197,20 @@ struct bus_type platform_bus_type = {
>   };
>   EXPORT_SYMBOL_GPL(platform_bus_type);
>   
> +/**
> + * platform_find_device_by_driver - Find a platform device with a given

Nit: "with" is easy to misinterpret there - my initial reaction to 
looking at this was "so why not just use driver_find_device()?". Maybe 
"which would match" might make it a bit clearer?

Robin.

> + * driver.
> + * @start: The device to start the search from.
> + * @drv: The device driver to look for.
> + */
> +struct device *platform_find_device_by_driver(struct device *start,
> +					      const struct device_driver *drv)
> +{
> +	return bus_find_device(&platform_bus_type, start, drv,
> +			       (void *)platform_match);
> +}
> +EXPORT_SYMBOL_GPL(platform_find_device_by_driver);
> +
>   int __init platform_bus_init(void)
>   {
>   	int error;
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> index 58baf49d9926..badab94be2d6 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
> @@ -242,9 +242,7 @@ static struct component_match *exynos_drm_match_add(struct device *dev)
>   		if (!info->driver || !(info->flags & DRM_COMPONENT_DRIVER))
>   			continue;
>   
> -		while ((d = bus_find_device(&platform_bus_type, p,
> -					    &info->driver->driver,
> -					    (void *)platform_bus_type.match))) {
> +		while ((d = platform_find_device_by_driver(p, &info->driver->driver))) {
>   			put_device(p);
>   
>   			if (!(info->flags & DRM_FIMC_DEVICE) ||
> @@ -412,9 +410,8 @@ static void exynos_drm_unregister_devices(void)
>   		if (!info->driver || !(info->flags & DRM_VIRTUAL_DEVICE))
>   			continue;
>   
> -		while ((dev = bus_find_device(&platform_bus_type, NULL,
> -					    &info->driver->driver,
> -					    (void *)platform_bus_type.match))) {
> +		while ((dev = platform_find_device_by_driver(NULL,
> +						&info->driver->driver))) {
>   			put_device(dev);
>   			platform_device_unregister(to_platform_device(dev));
>   		}
> diff --git a/drivers/gpu/drm/mcde/mcde_drv.c b/drivers/gpu/drm/mcde/mcde_drv.c
> index baf63fb6850a..c07abf9e201c 100644
> --- a/drivers/gpu/drm/mcde/mcde_drv.c
> +++ b/drivers/gpu/drm/mcde/mcde_drv.c
> @@ -477,8 +477,7 @@ static int mcde_probe(struct platform_device *pdev)
>   		struct device_driver *drv = &mcde_component_drivers[i]->driver;
>   		struct device *p = NULL, *d;
>   
> -		while ((d = bus_find_device(&platform_bus_type, p, drv,
> -					    (void *)platform_bus_type.match))) {
> +		while ((d = platform_find_device_by_driver(p, drv))) {
>   			put_device(p);
>   			component_match_add(dev, &match, mcde_compare_dev, d);
>   			p = d;
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> index 53d2c5bd61dc..38dc26376961 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> @@ -330,8 +330,7 @@ static struct component_match *rockchip_drm_match_add(struct device *dev)
>   		struct device *p = NULL, *d;
>   
>   		do {
> -			d = bus_find_device(&platform_bus_type, p, &drv->driver,
> -					    (void *)platform_bus_type.match);
> +			d = platform_find_device_by_driver(p, &drv->driver);
>   			put_device(p);
>   			p = d;
>   
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.c b/drivers/gpu/drm/vc4/vc4_drv.c
> index bf11930e40e1..1551c8253bec 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.c
> +++ b/drivers/gpu/drm/vc4/vc4_drv.c
> @@ -237,8 +237,7 @@ static void vc4_match_add_drivers(struct device *dev,
>   		struct device_driver *drv = &drivers[i]->driver;
>   		struct device *p = NULL, *d;
>   
> -		while ((d = bus_find_device(&platform_bus_type, p, drv,
> -					    (void *)platform_bus_type.match))) {
> +		while ((d = platform_find_device_by_driver(p, drv))) {
>   			put_device(p);
>   			component_match_add(dev, match, compare_dev, d);
>   			p = d;
> diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> index 9bc36b589827..37e15a935a42 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -51,6 +51,9 @@ extern struct device platform_bus;
>   extern void arch_setup_pdev_archdata(struct platform_device *);
>   extern struct resource *platform_get_resource(struct platform_device *,
>   					      unsigned int, unsigned int);
> +extern struct device *
> +platform_find_device_by_driver(struct device *start,
> +			       const struct device_driver *drv);
>   extern void __iomem *
>   devm_platform_ioremap_resource(struct platform_device *pdev,
>   			       unsigned int index);
>