Re: [PATCH 1/2] drm/bridge: Support finding bridge with struct device

Jani Nikula
2024-05-15T09:39:44Z

On Tue, 14 May 2024, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
> The pointer of 'struct device' can also be used as a key to search drm
> bridge instance from the global bridge list, traditionally, fwnode and
> 'OF' based APIs requires the system has decent fwnode/OF Graph support.
> While the drm_find_bridge_by_dev() function introduced in this series
> don't has such a restriction. It only require you has a pointer to the
> backing device. Hence, it may suitable for some small and/or limited
> display subsystems.
>
> Also add the drm_bridge_add_with_dev() as a helper, which automatically
> set the .of_node field of drm_bridge instances if you call it. But it
> suitable for simple bridge drivers which one device backing one drm_bridge
> instance.
>
> Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
> ---
> drivers/gpu/drm/drm_bridge.c | 39 ++++++++++++++++++++++++++++++++++++
> include/drm/drm_bridge.h | 5 +++++
> 2 files changed, 44 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 584d109330ab..1928d9d0dd3c 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -213,6 +213,23 @@ void drm_bridge_add(struct drm_bridge *bridge)
> }
> EXPORT_SYMBOL(drm_bridge_add);
>
> +/**
> + * drm_bridge_add_with_dev - add the given bridge to the global bridge list
> + *
> + * @bridge: bridge control structure
> + * @dev: pointer to the kernel device that this bridge is backed.
> + */
> +void drm_bridge_add_with_dev(struct drm_bridge *bridge, struct device *dev)
> +{
> + if (dev) {
> + bridge->kdev = dev;
> + bridge->of_node = dev->of_node;
> + }
> +
> + drm_bridge_add(bridge);
> +}
> +EXPORT_SYMBOL_GPL(drm_bridge_add_with_dev);

I don't actually have an opinion on whether the dev parameter is useful
or not.

But please don't add a drm_bridge_add_with_dev() and then convert more
than half the drm_bridge_add() users to that. Please just add a struct
device *dev parameter to drm_bridge_add(), and pass NULL if it's not
relevant.

BR,
Jani.

> +
> static void drm_bridge_remove_void(void *bridge)
> {
> drm_bridge_remove(bridge);
> @@ -1334,6 +1351,27 @@ void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> }
> EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
>
> +struct drm_bridge *drm_find_bridge_by_dev(struct device *kdev)
> +{
> + struct drm_bridge *bridge;
> +
> + if (!kdev)
> + return NULL;
> +
> + mutex_lock(&bridge_lock);
> +
> + list_for_each_entry(bridge, &bridge_list, list) {
> + if (bridge->kdev == kdev) {
> + mutex_unlock(&bridge_lock);
> + return bridge;
> + }
> + }
> +
> + mutex_unlock(&bridge_lock);
> + return NULL;
> +}
> +EXPORT_SYMBOL_GPL(drm_find_bridge_by_dev);
> +
> #ifdef CONFIG_OF
> /**
> * of_drm_find_bridge - find the bridge corresponding to the device node in
> @@ -1361,6 +1399,7 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np)
> return NULL;
> }
> EXPORT_SYMBOL(of_drm_find_bridge);
> +
> #endif
>
> MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@samsung.com>");
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 4baca0d9107b..70d8393bbd9c 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -715,6 +715,8 @@ struct drm_bridge {
> struct drm_private_obj base;
> /** @dev: DRM device this bridge belongs to */
> struct drm_device *dev;
> + /** @kdev: pointer to the kernel device backing this bridge */
> + struct device *kdev;
> /** @encoder: encoder to which this bridge is connected */
> struct drm_encoder *encoder;
> /** @chain_node: used to form a bridge chain */
> @@ -782,12 +784,15 @@ drm_priv_to_bridge(struct drm_private_obj *priv)
> }
>
> void drm_bridge_add(struct drm_bridge *bridge);
> +void drm_bridge_add_with_dev(struct drm_bridge *bridge, struct device *dev);
> int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge);
> void drm_bridge_remove(struct drm_bridge *bridge);
> int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> struct drm_bridge *previous,
> enum drm_bridge_attach_flags flags);
>
> +struct drm_bridge *drm_find_bridge_by_dev(struct device *kdev);
> +
> #ifdef CONFIG_OF
> struct drm_bridge *of_drm_find_bridge(struct device_node *np);
> #else

--
Jani Nikula, Intel