[PATCH] drm/imx: imx-ldb: Accept drm_of_find_panel_or_bridge failure

[PATCH] drm/imx: imx-ldb: Accept drm_of_find_panel_or_bridge failure

[Leonard Crestez]

Not having an endpoint bound in DT should not cause a failure here,
there are fallbacks. So let's explicitly accept a missing endpoint.

This behavior change was introduced by refactoring in drm_of parsing
code and it should not require dts changes.

In particular this fixes imx6qdl-sabreauto boards.

Link: https://lists.freedesktop.org/archives/dri-devel/2017-May/141233.html
Fixes: ebc944613567 ("drm: convert drivers to use drm_of_find_panel_or_bridge")
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>

---

This relies on drm_of_find_panel_or_bridge returning -ENODEV
specifically if no remote is found for the endpoint. This behavior can
be seen by looking at the code but is not otherwise obviously
guaranteed.

Perhaps this should be explicitly mentioned in that function's
documentation?

 drivers/gpu/drm/imx/imx-ldb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index 8fb801f..4c8a521 100644
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -673,7 +673,7 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
 		ret = drm_of_find_panel_or_bridge(child,
 						  imx_ldb->lvds_mux ? 4 : 2, 0,
 						  &channel->panel, &channel->bridge);
-		if (ret)
+		if (ret != -ENODEV)
 			return ret;
 
 		/* panel ddc only if there is no bridge */
-- 
2.7.4

Re: [PATCH] drm/imx: imx-ldb: Accept drm_of_find_panel_or_bridge failure

[Philipp Zabel]

Hi Leonard,

thank you for the patch. Comment below.

On Wed, 2017-05-10 at 13:57 +0300, Leonard Crestez wrote:
> Not having an endpoint bound in DT should not cause a failure here,
> there are fallbacks. So let's explicitly accept a missing endpoint.
> 
> This behavior change was introduced by refactoring in drm_of parsing
> code and it should not require dts changes.
> 
> In particular this fixes imx6qdl-sabreauto boards.
> 
> Link: https://lists.freedesktop.org/archives/dri-devel/2017-May/141233.html
> Fixes: ebc944613567 ("drm: convert drivers to use drm_of_find_panel_or_bridge")
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> 
> ---
> 
> This relies on drm_of_find_panel_or_bridge returning -ENODEV
> specifically if no remote is found for the endpoint. This behavior can
> be seen by looking at the code but is not otherwise obviously
> guaranteed.
> 
> Perhaps this should be explicitly mentioned in that function's
> documentation?
> 
>  drivers/gpu/drm/imx/imx-ldb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
> index 8fb801f..4c8a521 100644
> --- a/drivers/gpu/drm/imx/imx-ldb.c
> +++ b/drivers/gpu/drm/imx/imx-ldb.c
> @@ -673,7 +673,7 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
>  		ret = drm_of_find_panel_or_bridge(child,
>  						  imx_ldb->lvds_mux ? 4 : 2, 0,
>  						  &channel->panel, &channel->bridge);
> -		if (ret)
> +		if (ret != -ENODEV)

That should be
	if (ret && ret != -ENODEV)
as we don't want to return here if a panel or bridge was found.

regards
Philipp