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SubjectRe: [PATCH v2 26/26] drm/bridge: establish a link between the bridge supplier and consumer
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On 04.05.2018 15:52, Peter Rosin wrote:
> If the bridge supplier is unbound, this will bring the bridge consumer
> down along with the bridge. Thus, there will no longer linger any
> dangling pointers from the bridge consumer (the drm_device) to some
> non-existent bridge supplier.
>
> Signed-off-by: Peter Rosin <peda@axentia.se>
> ---
> drivers/gpu/drm/drm_bridge.c | 18 ++++++++++++++++++
> include/drm/drm_bridge.h | 2 ++
> 2 files changed, 20 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 78d186b6831b..0259f0a3ff27 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -26,6 +26,7 @@
> #include <linux/mutex.h>
>
> #include <drm/drm_bridge.h>
> +#include <drm/drm_device.h>
> #include <drm/drm_encoder.h>
>
> #include "drm_crtc_internal.h"
> @@ -127,12 +128,25 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> if (bridge->dev)
> return -EBUSY;
>
> + if (encoder->dev->dev != bridge->odev) {

I wonder why device_link_add does not handle this case (self dependency)
silently as noop, as it seems to be a correct behavior.

> + bridge->link = device_link_add(encoder->dev->dev,
> + bridge->odev, 0);
> + if (!bridge->link) {
> + dev_err(bridge->odev, "failed to link bridge to %s\n",
> + dev_name(encoder->dev->dev));
> + return -EINVAL;
> + }
> + }
> +
> bridge->dev = encoder->dev;
> bridge->encoder = encoder;
>
> if (bridge->funcs->attach) {
> ret = bridge->funcs->attach(bridge);
> if (ret < 0) {
> + if (bridge->link)
> + device_link_del(bridge->link);
> + bridge->link = NULL;
> bridge->dev = NULL;
> bridge->encoder = NULL;
> return ret;
> @@ -159,6 +173,10 @@ void drm_bridge_detach(struct drm_bridge *bridge)
> if (bridge->funcs->detach)
> bridge->funcs->detach(bridge);
>
> + if (bridge->link)
> + device_link_del(bridge->link);
> + bridge->link = NULL;
> +
> bridge->dev = NULL;
> }
>
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index b656e505d11e..804189c63a4c 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -261,6 +261,7 @@ struct drm_bridge_timings {
> * @list: to keep track of all added bridges
> * @timings: the timing specification for the bridge, if any (may
> * be NULL)
> + * @link: drm consumer <-> bridge supplier

Nitpick: "<->" suggests symmetry, maybe "device link from drm consumer
to the bridge" would be better.

Anyway:
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej

> * @funcs: control functions
> * @driver_private: pointer to the bridge driver's internal context
> */
> @@ -271,6 +272,7 @@ struct drm_bridge {
> struct drm_bridge *next;
> struct list_head list;
> const struct drm_bridge_timings *timings;
> + struct device_link *link;
>
> const struct drm_bridge_funcs *funcs;
> void *driver_private;


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