[PATCH] drm/cma-helper: fixup compilation

[Daniel Vetter]

On Tue, Feb 19, 2013 at 8:43 AM, Thierry Reding
<thierry.reding at avionic-design.de> wrote:
> On Fri, Feb 15, 2013 at 11:24:35AM +0100, Daniel Vetter wrote:
>> /me grabs a few brown paper bags
>>
>> So it looks like I've broken compilation in
>>
>> commit 6aed8ec3f76a22217c9ae183d32b1aa990bed069
>> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
>> Date:   Sun Jan 20 17:32:21 2013 +0100
>>
>>     drm: review locking for drm_fb_helper_restore_fbdev_mode
>>
>> Fix it up again.
>>
>> Reported-by: Wu Fengguang <fengguang.wu at intel.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>> ---
>>  drivers/gpu/drm/drm_fb_cma_helper.c |    2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
>> index e851658..ef68e34 100644
>> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>> @@ -377,6 +377,8 @@ EXPORT_SYMBOL_GPL(drm_fbdev_cma_fini);
>>   */
>>  void drm_fbdev_cma_restore_mode(struct drm_fbdev_cma *fbdev_cma)
>>  {
>> +     struct drm_device *dev = fbdev_cma->fb_helper.dev;
>> +
>>       drm_modeset_lock_all(dev);
>>       if (fbdev_cma)
>>               drm_fb_helper_restore_fbdev_mode(&fbdev_cma->fb_helper);
>
> The above check indicates that fbdev_cma might be NULL, so you're
> potentially dereferencing NULL when assigning the dev variable.

Right, looks like a need more brown-paper bags.

> Perhaps a better way would be to move the locking into the if block, as
> in the patch below.

Otoh I think it's a bit funny that you can pass NULL to restore_mode
and hotplug_event in the cma fb helper code. Imo it would be better to
just ditch those checks ... Laurent? I'll update the patch meanwhile.
-Daniel

>
> Thierry
>
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index e851658..54a250f 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -377,10 +377,11 @@ EXPORT_SYMBOL_GPL(drm_fbdev_cma_fini);
>   */
>  void drm_fbdev_cma_restore_mode(struct drm_fbdev_cma *fbdev_cma)
>  {
> -       drm_modeset_lock_all(dev);
> -       if (fbdev_cma)
> +       if (fbdev_cma) {
> +               drm_modeset_lock_all(fbdev_cma->fb_helper.dev);
>                 drm_fb_helper_restore_fbdev_mode(&fbdev_cma->fb_helper);
> -       drm_modeset_unlock_all(dev);
> +               drm_modeset_unlock_all(fbdev_cma->fb_helper.dev);
> +       }
>  }
>  EXPORT_SYMBOL_GPL(drm_fbdev_cma_restore_mode);



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch