Hello Thomas, Thanks a lot for your feedback. On 2/1/22 10:59, Thomas Zimmermann wrote: > Hi > > Am 31.01.22 um 21:12 schrieb Javier Martinez Canillas: >> Add support to convert 8-bit grayscale to reversed monochrome for drivers >> that control monochromatic displays, that only have 1 bit per pixel depth. >> >> This helper function was based on repaper_gray8_to_mono_reversed() from >> the drivers/gpu/drm/tiny/repaper.c driver. > > You could convert repaper to the new helper. > Yes, I plan to do it but was out of scope for this patch series. >> >> Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> >> --- >> >> drivers/gpu/drm/drm_format_helper.c | 35 +++++++++++++++++++++++++++++ >> include/drm/drm_format_helper.h | 2 ++ >> 2 files changed, 37 insertions(+) >> >> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c >> index 0f28dd2bdd72..bf477c136082 100644 >> --- a/drivers/gpu/drm/drm_format_helper.c >> +++ b/drivers/gpu/drm/drm_format_helper.c >> @@ -584,3 +584,38 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for >> return -EINVAL; >> } >> EXPORT_SYMBOL(drm_fb_blit_toio); >> + >> +/** >> + * drm_fb_gray8_to_mono_reversed - Convert grayscale to reversed monochrome >> + * @dst: reversed monochrome destination buffer >> + * @src: 8-bit grayscale source buffer >> + * @clip: Clip rectangle area to copy >> + * >> + * DRM doesn't have native monochrome or grayscale support. >> + * Such drivers can announce the commonly supported XR24 format to userspace >> + * and use drm_fb_xrgb8888_to_gray8() to convert to grayscale and then this >> + * helper function to convert to the native format. >> + */ >> +void drm_fb_gray8_to_mono_reversed(void *dst, void *src, const struct drm_rect *clip) > > IMHO it would be better to have a function that converts xrgb8888 to > mono and let it handle the intermediate step of gray8. > That's a good idea. I'll add that too. >> +{ >> + size_t width = drm_rect_width(clip); >> + size_t height = drm_rect_width(clip); >> + >> + u8 *mono = dst, *gray8 = src; >> + unsigned int y, xb, i; >> + >> + for (y = 0; y < height; y++) >> + for (xb = 0; xb < width / 8; xb++) { > > The inner loop should probably go into a separate helper function. See > the drm_fb_*_line() helpers in this file > > At some point, we's want to have a single blit helper that takes source > and destination formats/buffers. It would then pick the correct per-line > helper for the conversion. So yeah, we'd want something composable. > Agreed. I'll split that into a separate helper function. Best regards, -- Javier Martinez Canillas Linux Engineering Red Hat