[PATCH v2 0/2] drm: fix some bridge api misunderstandings

[PATCH v2 0/2] drm: fix some bridge api misunderstandings

[Peter Rosin]

Hi!

The first patch was forgotten, so I improved the commit message based
on the discussion from last time, and then added a patch with a
requested documentation update.

See https://lkml.org/lkml/2018/5/2/81

Cheers,
Peter

Peter Rosin (2):
  drm/sti: do not remove the drm_bridge that was never added
  drm: bridge: document bridge attach/detach imbalance

 drivers/gpu/drm/drm_bridge.c   | 4 ++++
 drivers/gpu/drm/sti/sti_hda.c  | 1 -
 drivers/gpu/drm/sti/sti_hdmi.c | 1 -
 3 files changed, 4 insertions(+), 2 deletions(-)

-- 
2.11.0

[PATCH v2 1/2] drm/sti: do not remove the drm_bridge that was never added

[Peter Rosin]

Removing the drm_bridge_remove call should avoid a NULL dereference
during list processing in drm_bridge_remove if the error path is ever
taken.

The more natural approach would perhaps be to add a drm_bridge_add,
but there are several other bridges that never call drm_bridge_add.
Just removing the drm_bridge_remove is the easier fix.

Fixes: 84601dbdea36 ("drm: sti: rework init sequence")
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Peter Rosin <peda@axentia.se>
---
 drivers/gpu/drm/sti/sti_hda.c  | 1 -
 drivers/gpu/drm/sti/sti_hdmi.c | 1 -
 2 files changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/sti/sti_hda.c b/drivers/gpu/drm/sti/sti_hda.c
index 67bbdb49fffc..199db13f565c 100644
--- a/drivers/gpu/drm/sti/sti_hda.c
+++ b/drivers/gpu/drm/sti/sti_hda.c
@@ -721,7 +721,6 @@ static int sti_hda_bind(struct device *dev, struct device *master, void *data)
 	return 0;
 
 err_sysfs:
-	drm_bridge_remove(bridge);
 	return -EINVAL;
 }
 
diff --git a/drivers/gpu/drm/sti/sti_hdmi.c b/drivers/gpu/drm/sti/sti_hdmi.c
index 58f431102512..932724784942 100644
--- a/drivers/gpu/drm/sti/sti_hdmi.c
+++ b/drivers/gpu/drm/sti/sti_hdmi.c
@@ -1315,7 +1315,6 @@ static int sti_hdmi_bind(struct device *dev, struct device *master, void *data)
 	return 0;
 
 err_sysfs:
-	drm_bridge_remove(bridge);
 	hdmi->drm_connector = NULL;
 	return -EINVAL;
 }
-- 
2.11.0

[PATCH v2 2/2] drm: bridge: document bridge attach/detach imbalance

[Peter Rosin]

Since 4a878c03d562 ("drm: bridge: Detach bridge from encoder at encoder
cleanup time"), it is generally no longer correct to detach bridges from
encoders manually. Document that.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
 drivers/gpu/drm/drm_bridge.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 1638bfe9627c..ba7025041e46 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -104,6 +104,10 @@ EXPORT_SYMBOL(drm_bridge_remove);
  * If non-NULL the previous bridge must be already attached by a call to this
  * function.
  *
+ * Note that bridges attached to encoders are auto-detached during encoder
+ * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
+ * *not* be balanced with a drm_bridge_detach() in driver code.
+ *
  * RETURNS:
  * Zero on success, error code on failure
  */
-- 
2.11.0

Re: [PATCH v2 1/2] drm/sti: do not remove the drm_bridge that was never added

[Benjamin Gaignard]

2018-08-06 8:19 GMT+02:00 Peter Rosin <peda@axentia.se>:
> Removing the drm_bridge_remove call should avoid a NULL dereference
> during list processing in drm_bridge_remove if the error path is ever
> taken.
>
> The more natural approach would perhaps be to add a drm_bridge_add,
> but there are several other bridges that never call drm_bridge_add.
> Just removing the drm_bridge_remove is the easier fix.
>
> Fixes: 84601dbdea36 ("drm: sti: rework init sequence")
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Peter Rosin <peda@axentia.se>

Pushed on drm-misc-next,

Thanks,
Benjamin

> ---
>  drivers/gpu/drm/sti/sti_hda.c  | 1 -
>  drivers/gpu/drm/sti/sti_hdmi.c | 1 -
>  2 files changed, 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/sti/sti_hda.c b/drivers/gpu/drm/sti/sti_hda.c
> index 67bbdb49fffc..199db13f565c 100644
> --- a/drivers/gpu/drm/sti/sti_hda.c
> +++ b/drivers/gpu/drm/sti/sti_hda.c
> @@ -721,7 +721,6 @@ static int sti_hda_bind(struct device *dev, struct device *master, void *data)
>         return 0;
>
>  err_sysfs:
> -       drm_bridge_remove(bridge);
>         return -EINVAL;
>  }
>
> diff --git a/drivers/gpu/drm/sti/sti_hdmi.c b/drivers/gpu/drm/sti/sti_hdmi.c
> index 58f431102512..932724784942 100644
> --- a/drivers/gpu/drm/sti/sti_hdmi.c
> +++ b/drivers/gpu/drm/sti/sti_hdmi.c
> @@ -1315,7 +1315,6 @@ static int sti_hdmi_bind(struct device *dev, struct device *master, void *data)
>         return 0;
>
>  err_sysfs:
> -       drm_bridge_remove(bridge);
>         hdmi->drm_connector = NULL;
>         return -EINVAL;
>  }
> --
> 2.11.0
>

Re: [PATCH v2 2/2] drm: bridge: document bridge attach/detach imbalance

[Andrzej Hajda]

On 06.08.2018 08:19, Peter Rosin wrote:
> Since 4a878c03d562 ("drm: bridge: Detach bridge from encoder at encoder
> cleanup time"), it is generally no longer correct to detach bridges from
> encoders manually. Document that.
>
> Signed-off-by: Peter Rosin <peda@axentia.se>
> ---
>  drivers/gpu/drm/drm_bridge.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 1638bfe9627c..ba7025041e46 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -104,6 +104,10 @@ EXPORT_SYMBOL(drm_bridge_remove);
>   * If non-NULL the previous bridge must be already attached by a call to this
>   * function.
>   *
> + * Note that bridges attached to encoders are auto-detached during encoder
> + * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
> + * *not* be balanced with a drm_bridge_detach() in driver code.
> + *
>   * RETURNS:
>   * Zero on success, error code on failure
>   */

Pushed to drm-misc-next.

--
Regards
Andrzej