2023-03-10 18:41:36

by Hamza Mahfooz

Subject: [PATCH v2] drm/amd/display: use a more accurate check in dm_helpers_dp_read_dpcd()

We should be checking if drm_dp_dpcd_read() returns the size that we are
asking it to read instead of just checking if it is greater than zero.
So, compare the return value of drm_dp_dpcd_read() to the requested
read size.

Signed-off-by: Hamza Mahfooz <[email protected]>
---
v2: drop the WARN_ON().
---
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 8d598b322e5b..9c1e91c2179e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -511,8 +511,8 @@ bool dm_helpers_dp_read_dpcd(
return false;
}

- return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address,
- data, size) > 0;
+ return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, data,
+ size) == size;
}

bool dm_helpers_dp_write_dpcd(
--
2.39.2

2023-03-20 20:22:13

by Harry Wentland

Subject: Re: [PATCH v2] drm/amd/display: use a more accurate check in dm_helpers_dp_read_dpcd()

On 3/10/23 13:42, Hamza Mahfooz wrote:
> We should be checking if drm_dp_dpcd_read() returns the size that we are
> asking it to read instead of just checking if it is greater than zero.
> So, compare the return value of drm_dp_dpcd_read() to the requested
> read size.
>
> Signed-off-by: Hamza Mahfooz <[email protected]>

I don't think we can ever hit a case where the return value is greater
than 0 but not equal to size as drm_dp_dpcd_access already checks for it.

Either way, the stricter check makes sense and is
Reviewed-by: Harry Wentland <[email protected]>

Harry

> ---
> v2: drop the WARN_ON().
> ---
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> index 8d598b322e5b..9c1e91c2179e 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> @@ -511,8 +511,8 @@ bool dm_helpers_dp_read_dpcd(
> return false;
> }
>
> - return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address,
> - data, size) > 0;
> + return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, data,
> + size) == size;
> }
>
> bool dm_helpers_dp_write_dpcd(