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SubjectRe: [PATCH 5/5] drm/stm: ltdc: add support of ycbcr pixel formats
From
Hi Nathan,

On 2/2/22 17:54, Nathan Chancellor wrote:
> Hi Yannick,
>
> On Wed, Dec 15, 2021 at 10:48:43PM +0100, Yannick Fertre wrote:
>> This patch adds the following YCbCr input pixel formats on the latest
>> LTDC hardware version:
>>
>> 1 plane (co-planar) : YUYV, YVYU, UYVY, VYUY
>> 2 planes (semi-planar): NV12, NV21
>> 3 planes (full-planar): YU12=I420=DRM YUV420, YV12=DRM YVU420
>>
>> Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
>
> <snip>
>
>> +static inline void ltdc_set_ycbcr_config(struct drm_plane *plane, u32 drm_pix_fmt)
>> +{
>> + struct ltdc_device *ldev = plane_to_ltdc(plane);
>> + struct drm_plane_state *state = plane->state;
>> + u32 lofs = plane->index * LAY_OFS;
>> + u32 val;
>> +
>> + switch (drm_pix_fmt) {
>> + case DRM_FORMAT_YUYV:
>> + val = (YCM_I << 4) | LxPCR_YF | LxPCR_CBF;
>> + break;
>> + case DRM_FORMAT_YVYU:
>> + val = (YCM_I << 4) | LxPCR_YF;
>> + break;
>> + case DRM_FORMAT_UYVY:
>> + val = (YCM_I << 4) | LxPCR_CBF;
>> + break;
>> + case DRM_FORMAT_VYUY:
>> + val = (YCM_I << 4);
>> + break;
>> + case DRM_FORMAT_NV12:
>> + val = (YCM_SP << 4) | LxPCR_CBF;
>> + break;
>> + case DRM_FORMAT_NV21:
>> + val = (YCM_SP << 4);
>> + break;
>> + case DRM_FORMAT_YUV420:
>> + case DRM_FORMAT_YVU420:
>> + val = (YCM_FP << 4);
>> + break;
>> + default:
>> + /* RGB or not a YCbCr supported format */
>> + break;
>> + }
>> +
>> + /* Enable limited range */
>> + if (state->color_range == DRM_COLOR_YCBCR_LIMITED_RANGE)
>> + val |= LxPCR_YREN;
>> +
>> + /* enable ycbcr conversion */
>> + val |= LxPCR_YCEN;
>> +
>> + regmap_write(ldev->regmap, LTDC_L1PCR + lofs, val);
>> +}
>
> This patch as commit 484e72d3146b ("drm/stm: ltdc: add support of ycbcr
> pixel formats") in -next introduced the following clang warning:
>
> drivers/gpu/drm/stm/ltdc.c:625:2: warning: variable 'val' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
> default:
> ^~~~~~~
> drivers/gpu/drm/stm/ltdc.c:635:2: note: uninitialized use occurs here
> val |= LxPCR_YCEN;
> ^~~
> drivers/gpu/drm/stm/ltdc.c:600:9: note: initialize the variable 'val' to silence this warning
> u32 val;
> ^
> = 0
> 1 warning generated.
>
> Would it be okay to just return in the default case (maybe with a
> message about an unsupported format?) or should there be another fix?
>
> Cheers,


Thanks for your help.
It'okay for a message for unsupported format with a return in the
default case.
Do you want create & push the patch?

Best regards

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