diff mbox series

[v3,1/6] drm/rockchip: vop2: initialize possible_crtcs properly

Message ID 20230124054706.3921383-2-michael.riesch@wolfvision.net
State New
Headers
Series drm/rockchip: vop2: add support for the rgb output block |

Commit Message

Michael Riesch Jan. 24, 2023, 5:47 a.m. UTC 
  The variable possible_crtcs is only initialized for primary and
overlay planes. Since the VOP2 driver only supports these plane
types at the moment, the current code is safe. However, in order
to provide a future-proof solution, fix the initialization of
the variable.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Michael Riesch <michael.riesch@wolfvision.net>
---
v3:
 - no changes
v2:
 - new patch

 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Nathan Chancellor March 14, 2023, 4:08 p.m. UTC | #1 
Hi Michael,

On Tue, Jan 24, 2023 at 06:47:01AM +0100, Michael Riesch wrote:
> The variable possible_crtcs is only initialized for primary and
> overlay planes. Since the VOP2 driver only supports these plane
> types at the moment, the current code is safe. However, in order
> to provide a future-proof solution, fix the initialization of
> the variable.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <error27@gmail.com>
> Signed-off-by: Michael Riesch <michael.riesch@wolfvision.net>
> ---
> v3:
>  - no changes
> v2:
>  - new patch
> 
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> index 8cecf81a5ae0..374ef821b453 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> @@ -2322,10 +2322,11 @@ static int vop2_create_crtc(struct vop2 *vop2)
>  				/* change the unused primary window to overlay window */
>  				win->type = DRM_PLANE_TYPE_OVERLAY;
>  			}
> -		}
> -
> -		if (win->type == DRM_PLANE_TYPE_OVERLAY)
> +		} else if (win->type == DRM_PLANE_TYPE_OVERLAY) {
>  			possible_crtcs = (1 << nvps) - 1;
> +		} else {
> +			possible_crtcs = 0;
> +		}
>  
>  		ret = vop2_plane_init(vop2, win, possible_crtcs);
>  		if (ret) {
> -- 
> 2.30.2
> 

This patch is now in -next as commit 368419a2d429 ("drm/rockchip: vop2:
initialize possible_crtcs properly") and it actually appears to
introduce a path where possible_crtcs could be used uninitialized.

  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2316:8: error: variable 'possible_crtcs' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
                          if (vp) {
                              ^~
  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2330:36: note: uninitialized use occurs here
                  ret = vop2_plane_init(vop2, win, possible_crtcs);
                                                   ^~~~~~~~~~~~~~
  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2316:4: note: remove the 'if' if its condition is always true
                          if (vp) {
                          ^~~~~~~~
  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2298:21: note: initialize the variable 'possible_crtcs' to silence this warning
                  u32 possible_crtcs;
                                    ^
                                     = 0
  1 error generated.

Prior to this change, if that else path was hit, clang recognized based on
the assignment that the next if statement would always be true. Now, if
the else path is taken, the possible_crtcs assignment will be missed. Is
that intentional?

Cheers,
Nathan
Michael Riesch March 15, 2023, 8:35 a.m. UTC | #2 
Hi Nathan,

On 3/14/23 17:08, Nathan Chancellor wrote:
> Hi Michael,
> 
> On Tue, Jan 24, 2023 at 06:47:01AM +0100, Michael Riesch wrote:
>> The variable possible_crtcs is only initialized for primary and
>> overlay planes. Since the VOP2 driver only supports these plane
>> types at the moment, the current code is safe. However, in order
>> to provide a future-proof solution, fix the initialization of
>> the variable.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Reported-by: Dan Carpenter <error27@gmail.com>
>> Signed-off-by: Michael Riesch <michael.riesch@wolfvision.net>
>> ---
>> v3:
>>  - no changes
>> v2:
>>  - new patch
>>
>>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> index 8cecf81a5ae0..374ef821b453 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> @@ -2322,10 +2322,11 @@ static int vop2_create_crtc(struct vop2 *vop2)
>>  				/* change the unused primary window to overlay window */
>>  				win->type = DRM_PLANE_TYPE_OVERLAY;
>>  			}
>> -		}
>> -
>> -		if (win->type == DRM_PLANE_TYPE_OVERLAY)
>> +		} else if (win->type == DRM_PLANE_TYPE_OVERLAY) {
>>  			possible_crtcs = (1 << nvps) - 1;
>> +		} else {
>> +			possible_crtcs = 0;
>> +		}
>>  
>>  		ret = vop2_plane_init(vop2, win, possible_crtcs);
>>  		if (ret) {
>> -- 
>> 2.30.2
>>
> 
> This patch is now in -next as commit 368419a2d429 ("drm/rockchip: vop2:
> initialize possible_crtcs properly") and it actually appears to
> introduce a path where possible_crtcs could be used uninitialized.
> 
>   drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2316:8: error: variable 'possible_crtcs' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>                           if (vp) {
>                               ^~
>   drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2330:36: note: uninitialized use occurs here
>                   ret = vop2_plane_init(vop2, win, possible_crtcs);
>                                                    ^~~~~~~~~~~~~~
>   drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2316:4: note: remove the 'if' if its condition is always true
>                           if (vp) {
>                           ^~~~~~~~
>   drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2298:21: note: initialize the variable 'possible_crtcs' to silence this warning
>                   u32 possible_crtcs;
>                                     ^
>                                      = 0
>   1 error generated.
> 
> Prior to this change, if that else path was hit, clang recognized based on
> the assignment that the next if statement would always be true. Now, if
> the else path is taken, the possible_crtcs assignment will be missed. Is
> that intentional?

As it turns out, the approach in my patch does not cover all paths. I'll
submit a follow-up patch that initializes possible_crtcs = 0 and drops
the else path. This should solve the issue for good.

Regards, Michael
diff mbox series

Patch

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index 8cecf81a5ae0..374ef821b453 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -2322,10 +2322,11 @@  static int vop2_create_crtc(struct vop2 *vop2)
 				/* change the unused primary window to overlay window */
 				win->type = DRM_PLANE_TYPE_OVERLAY;
 			}
-		}
-
-		if (win->type == DRM_PLANE_TYPE_OVERLAY)
+		} else if (win->type == DRM_PLANE_TYPE_OVERLAY) {
 			possible_crtcs = (1 << nvps) - 1;
+		} else {
+			possible_crtcs = 0;
+		}
 
 		ret = vop2_plane_init(vop2, win, possible_crtcs);
 		if (ret) {