On Tue, Aug 17, 2021 at 02:29:12PM +0200, Noralf Trønnes wrote:
> Add XRGB8888 emulation support for devices that can only do RGB332.
>
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_format_helper.c | 47 +++++++++++++++++++++++++++++
> include/drm/drm_format_helper.h | 2 ++
> 2 files changed, 49 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index 5231104b1498..53b426da7467 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -135,6 +135,53 @@ void drm_fb_swab(void *dst, void *src, struct drm_framebuffer *fb,
> }
> EXPORT_SYMBOL(drm_fb_swab);
>
> +static void drm_fb_xrgb8888_to_rgb332_line(u8 *dbuf, u32 *sbuf, unsigned int pixels)
> +{
> + unsigned int x;
> +
> + for (x = 0; x < pixels; x++)
> + dbuf[x] = ((sbuf[x] & 0x00e00000) >> 16) |
I think for 2/3 bits correct rounding would be useful, not just masking.
i.e. before you shift add 0x00100000 here, and similar below.
Also I just realized we've totally ignored endianess on these, which is
not great, because strictly speaking all the drm_fourcc codes should be
little endian. But I'm also not sure that's worth fixing ...
Either way, lgtm:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> + ((sbuf[x] & 0x0000e000) >> 11) |
> + ((sbuf[x] & 0x000000c0) >> 6);
> +}
> +
> +/**
> + * drm_fb_xrgb8888_to_rgb332 - Convert XRGB8888 to RGB332 clip buffer
> + * @dst: RGB332 destination buffer
> + * @src: XRGB8888 source buffer
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + *
> + * Drivers can use this function for RGB332 devices that don't natively support XRGB8888.
> + *
> + * This function does not apply clipping on dst, i.e. the destination is a small buffer
> + * containing the clip rect only.
> + */
> +void drm_fb_xrgb8888_to_rgb332(void *dst, void *src, struct drm_framebuffer *fb,
> + struct drm_rect *clip)
> +{
> + size_t width = drm_rect_width(clip);
> + size_t src_len = width * sizeof(u32);
> + unsigned int y;
> + void *sbuf;
> +
> + /* Use a buffer to speed up access on buffers with uncached read mapping (i.e. WC) */
> + sbuf = kmalloc(src_len, GFP_KERNEL);
> + if (!sbuf)
> + return;
> +
> + src += clip_offset(clip, fb->pitches[0], sizeof(u32));
> + for (y = 0; y < drm_rect_height(clip); y++) {
> + memcpy(sbuf, src, src_len);
> + drm_fb_xrgb8888_to_rgb332_line(dst, sbuf, width);
> + src += fb->pitches[0];
> + dst += width;
> + }
> +
> + kfree(sbuf);
> +}
> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb332);
> +
> static void drm_fb_xrgb8888_to_rgb565_line(u16 *dbuf, u32 *sbuf,
> unsigned int pixels,
> bool swab)
> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> index 4e0258a61311..d0809aff5cf8 100644
> --- a/include/drm/drm_format_helper.h
> +++ b/include/drm/drm_format_helper.h
> @@ -16,6 +16,8 @@ void drm_fb_memcpy_dstclip(void __iomem *dst, unsigned int dst_pitch, void *vadd
> struct drm_rect *clip);
> void drm_fb_swab(void *dst, void *src, struct drm_framebuffer *fb,
> struct drm_rect *clip, bool cached);
> +void drm_fb_xrgb8888_to_rgb332(void *dst, void *vaddr, struct drm_framebuffer *fb,
> + struct drm_rect *clip);
> void drm_fb_xrgb8888_to_rgb565(void *dst, void *vaddr,
> struct drm_framebuffer *fb,
> struct drm_rect *clip, bool swab);
> --
> 2.32.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
