Re: [PATCH libdrm] libdrm: update drm/drm_fourcc.h from kernel to add multi plane formats

[김승우 <sw0312.kim@samsung.com>]

Hi Ville,

I skipped explanation about NV12M and other two formats because these
formats are already in kernel drm_fourcc.h.

I think it is better to add a difference between NV12 and NV12M here.

NV12M has Y plane and CbCr plane and these are in non contiguous memory
region. Compared with NV12, NV12M's memory shape is like following.
NV12  : ______(Y)(CbCr)_______
NV12M : __(Y)_ ..... _(CbCr)__

Y and CbCr plane of NV12 can be expressed with one memory address and
offset of each plane. but NV12M needs memory address of each plane.

On 2012년 03월 30일 19:12, Ville Syrjälä wrote:
> On Fri, Mar 30, 2012 at 11:54:50AM +0900, Seung-Woo Kim wrote:
>> Multi buffer plane pixel formats are added as like kernel header.
>>
>> Signed-off-by: Seung-Woo Kim<sw0312.kim@samsung.com>
>> ---
>>   include/drm/drm_fourcc.h |    7 +++++++
>>   1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
>> index 85facb0..7cfd95a 100644
>> --- a/include/drm/drm_fourcc.h
>> +++ b/include/drm/drm_fourcc.h
>> @@ -107,6 +107,10 @@
>>   #define DRM_FORMAT_NV16		fourcc_code('N', 'V', '1', '6') /* 2x1 subsampled Cr:Cb plane */
>>   #define DRM_FORMAT_NV61		fourcc_code('N', 'V', '6', '1') /* 2x1 subsampled Cb:Cr plane */
>>
>> +/* 2 non contiguous plane YCbCr */
>> +#define DRM_FORMAT_NV12M	fourcc_code('N', 'M', '1', '2') /* 2x2 subsampled Cr:Cb plane */
> NAK. DRM_FORMAT_NV12 handles this just fine.
>

Exynos soc supports two kinds of memory shape explained above, so two
different types are need for exynos soc.

>> +#define DRM_FORMAT_NV12MT	fourcc_code('T', 'M', '1', '2') /* 2x2 subsampled Cr:Cb plane 64x32 macroblocks */
> This one is more difficult. Until now tiling was always handled in
> driver specific manner. OTOH if this format is really supported by
> different devices from multiple vendors, then it would probably
> make sense to add it as a standard format.
>
Exynos soc also supports normal and tiled pixel data and pixel data is 
shared
between hw blocks for example from scaler to hdmi.
So driver can not handle it internally.

IMHO, support for various shape can be helpful even though only exynos soc
family suppors these formats currently.

>> +
>>   /*
>>    * 3 plane YCbCr
>>    * index 0: Y plane, [7:0] Y
>> @@ -127,4 +131,7 @@
>>   #define DRM_FORMAT_YUV444	fourcc_code('Y', 'U', '2', '4') /* non-subsampled Cb (1) and Cr (2) planes */
>>   #define DRM_FORMAT_YVU444	fourcc_code('Y', 'V', '2', '4') /* non-subsampled Cr (1) and Cb (2) planes */
>>
>> +/* 3 non contiguous plane YCbCr */
>> +#define DRM_FORMAT_YUV420M	fourcc_code('Y', 'M', '1', '2') /* 2x2 subsampled Cb (1) and Cr (2) planes */a
> NAK. DRM_FORMAT_YUV420 handles this.

This is same with case of NV12M.

Regards.

-- 
Seung-Woo Kim
Samsung Software R&D Center
--


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