[PATCH] drm: add check for plane functions

[Shirish S]

On Fri, Mar 17, 2017 at 3:26 PM, Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
> On Fri, Mar 17, 2017 at 01:25:08PM +0530, Shirish S wrote:
>> update_plane() and disable_plane() functions
>> assoiciated with setting plane are called
>> without any check, causing kernel panic.
>
> Why are you registering a plane without the funcs?
>
Basically, enabling planes and making them fully functional is
generally a 2 -step process,
so i suggest for new drivers wanting to implement/re-design  planes,
would like to tap
the flow at enabling(listing caps) and later at ensuring it works.
I noticed that there is a underlying assumption only for
plane->(funcs) are implemented, whereas for
other function for crtc/connector/encoder function calls there is a
sanity check(or WARN_ON) through out the framework.

I believe this check wont cause any performance/functional impact.
Please let me know if am missing anything.
And further more help developers to focus on enabling planes via
various tests without causing reboots/system hangs.
>>
>> This patch adds the required check to avoid it.
>>
>> Change-Id: I0d6792608b33e674c217388aa57c4b7d680d9bc7
>> Signed-off-by: Shirish S <shirish.s at amd.com>
>> ---
>>  drivers/gpu/drm/drm_plane.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
>> index 249c0ae..f675f8b 100644
>> --- a/drivers/gpu/drm/drm_plane.c
>> +++ b/drivers/gpu/drm/drm_plane.c
>> @@ -456,6 +456,12 @@ static int __setplane_internal(struct drm_plane *plane,
>>  {
>>       int ret = 0;
>>
>> +     if (plane->funcs->disable_plane == NULL ||
>> +                             plane->funcs->update_plane == NULL) {
>> +             DRM_ERROR("plane funcs not implemented\n");
>> +             ret = -EPERM;
>> +             goto out;
>> +     }
>>       /* No fb means shut it down */
>>       if (!fb) {
>>               plane->old_fb = plane->fb;
>> --
>> 2.7.4
>>
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>
> --
> Ville Syrjälä
> Intel OTC