[PATCH v5 3/9] drm: verisilicon: add a driver for Verisilicon display controllers

[Thomas Zimmermann]

Hi

Am 22.01.26 um 10:47 schrieb Icenowy Zheng:
> 在 2026-01-21星期三的 13:56 +0100，Thomas Zimmermann写道：
>
> =================== 8< ====================
>>> +void drm_format_to_vs_format(u32 drm_format, struct vs_format
>>> *vs_format)
>>> +{
>>> +       switch (drm_format) {
>>> +       case DRM_FORMAT_XRGB4444:
>>> +       case DRM_FORMAT_RGBX4444:
>>> +       case DRM_FORMAT_XBGR4444:
>>> +       case DRM_FORMAT_BGRX4444:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_X4R4G4B4;
>>> +               break;
>>> +       case DRM_FORMAT_ARGB4444:
>>> +       case DRM_FORMAT_RGBA4444:
>>> +       case DRM_FORMAT_ABGR4444:
>>> +       case DRM_FORMAT_BGRA4444:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_A4R4G4B4;
>>> +               break;
>>> +       case DRM_FORMAT_XRGB1555:
>>> +       case DRM_FORMAT_RGBX5551:
>>> +       case DRM_FORMAT_XBGR1555:
>>> +       case DRM_FORMAT_BGRX5551:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_X1R5G5B5;
>>> +               break;
>>> +       case DRM_FORMAT_ARGB1555:
>>> +       case DRM_FORMAT_RGBA5551:
>>> +       case DRM_FORMAT_ABGR1555:
>>> +       case DRM_FORMAT_BGRA5551:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_A1R5G5B5;
>>> +               break;
>>> +       case DRM_FORMAT_RGB565:
>>> +       case DRM_FORMAT_BGR565:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_R5G6B5;
>>> +               break;
>>> +       case DRM_FORMAT_XRGB8888:
>>> +       case DRM_FORMAT_RGBX8888:
>>> +       case DRM_FORMAT_XBGR8888:
>>> +       case DRM_FORMAT_BGRX8888:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_X8R8G8B8;
>>> +               break;
>>> +       case DRM_FORMAT_ARGB8888:
>>> +       case DRM_FORMAT_RGBA8888:
>>> +       case DRM_FORMAT_ABGR8888:
>>> +       case DRM_FORMAT_BGRA8888:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_A8R8G8B8;
>>> +               break;
>>> +       case DRM_FORMAT_ARGB2101010:
>>> +       case DRM_FORMAT_RGBA1010102:
>>> +       case DRM_FORMAT_ABGR2101010:
>>> +       case DRM_FORMAT_BGRA1010102:
>>> +               vs_format->color = VSDC_COLOR_FORMAT_A2R10G10B10;
>>> +               break;
>>> +       default:
>>> +               DRM_WARN("Unexpected drm format!\n");
>> drm_warn(). If this can be invoked from user space,easily, better use
>> drm_dbg()
> This function is called during atomic_update of planes, and I think in
> this case the unknown formats should already be rejected because
> they're not advertised for any planes.
>
> Did I get it right on this?

Yes. In principle you should never reach the default case. This message 
is only for testing internally.

What I usually do is to compute such internal values in the atomic_check 
helper and then store them in the respective state. Here, you'd need a 
custom struct vs_plane_state to hold them. If the format conversion 
fails in atomic_check, it can still return an errno code to user space.

Doing this throughout the driver pushes all/most fail states before the 
'magic barrier.' [1]

[1] 
https://elixir.bootlin.com/linux/v6.19-rc5/source/drivers/gpu/drm/drm_atomic_helper.c#L2278


>
>>> +       }
>>> +
>>> +       switch (drm_format) {
>>> +       case DRM_FORMAT_RGBX4444:
>>> +       case DRM_FORMAT_RGBA4444:
>>> +       case DRM_FORMAT_RGBX5551:
>>> +       case DRM_FORMAT_RGBA5551:
>>> +       case DRM_FORMAT_RGBX8888:
>>> +       case DRM_FORMAT_RGBA8888:
>>> +       case DRM_FORMAT_RGBA1010102:
>>> +               vs_format->swizzle = VSDC_SWIZZLE_RGBA;
>>> +               break;
>>> +       case DRM_FORMAT_XBGR4444:
>>> +       case DRM_FORMAT_ABGR4444:
>>> +       case DRM_FORMAT_XBGR1555:
>>> +       case DRM_FORMAT_ABGR1555:
>>> +       case DRM_FORMAT_BGR565:
>>> +       case DRM_FORMAT_XBGR8888:
>>> +       case DRM_FORMAT_ABGR8888:
>>> +       case DRM_FORMAT_ABGR2101010:
>>> +               vs_format->swizzle = VSDC_SWIZZLE_ABGR;
>>> +               break;
>>> +       case DRM_FORMAT_BGRX4444:
>>> +       case DRM_FORMAT_BGRA4444:
>>> +       case DRM_FORMAT_BGRX5551:
>>> +       case DRM_FORMAT_BGRA5551:
>>> +       case DRM_FORMAT_BGRX8888:
>>> +       case DRM_FORMAT_BGRA8888:
>>> +       case DRM_FORMAT_BGRA1010102:
>>> +               vs_format->swizzle = VSDC_SWIZZLE_BGRA;
>>> +               break;
>>> +       default:
>>> +               /* N/A for YUV formats */
>>> +               vs_format->swizzle = VSDC_SWIZZLE_ARGB;
>>> +       }
>>> +
>>> +       /* N/A for non-YUV formats */
>>> +       vs_format->uv_swizzle = false;
>>> +}

These values could also go into vs_plane_state.

Best regard
Thomas


-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)