Messages in this thread | | | Date | Fri, 4 Feb 2022 17:00:16 +0100 | Subject | Re: [PATCH v2 1/4] drm/format-helper: Add drm_fb_{xrgb8888,gray8}_to_mono_reversed() | From | Thomas Zimmermann <> |
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Am 04.02.22 um 16:52 schrieb Thomas Zimmermann: [...] >> +/** >> + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed >> monochrome >> + * @dst: reversed monochrome destination buffer >> + * @dst_pitch: Number of bytes between two consecutive scanlines >> within dst >> + * @src: XRGB8888 source buffer >> + * @fb: DRM framebuffer >> + * @clip: Clip rectangle area to copy >> + * >> + * DRM doesn't have native monochrome support. >> + * Such drivers can announce the commonly supported XR24 format to >> userspace >> + * and use this function to convert to the native format. >> + * >> + * This function uses drm_fb_xrgb8888_to_gray8() to convert to >> grayscale and >> + * then the result is converted from grayscale to reversed monohrome. >> + */ >> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int >> dst_pitch, const void *src, >> + const struct drm_framebuffer *fb, >> + const struct drm_rect *clip) >> +{ >> + if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888)) >> + return; >> + >> + if (!dst_pitch) >> + dst_pitch = drm_rect_width(clip); >> + >> + drm_fb_xrgb8888_to_gray8(dst, dst_pitch, src, fb, clip); >> + drm_fb_gray8_to_mono_reversed(dst, dst_pitch, dst, fb, clip); > > Converting from dst into dst can give incorrect results. At some point > we probably want to add restrict qualifiers to these pointers, to help > the compiler with optimizing. > > A better approach here is to pull the per-line conversion from > drm_fb_xrgb8888_to_gray8() into a separate helper and implement a > line-by-line conversion here. something like this: > > drm_fb_xrgb8888_to_mono_reversed() > { > char *tmp = kmalloc(size of a single line of gray8) > > for (heigth) { > drm_fb_xrgb8888_to_gray8_line(tmp, ..., src, ...); > drm_fb_gray8_to_mono_reversed(dst, ..., tmp, ...);
Here, I meant 'drm_fb_gray8_to_mono_reversed_line()'
> > src += fb->pitches[0] > dst += dst_pitch; > } > > kfree(tmp); > }
To elaborate, this is an example of what I meant by composable. In the future, we can generalize this function and hand-in 2 function pointers the do the conversion with tmp as intermediate buffer. That would work for any combination of formats that have a common intermediate format.
> > Best regards > Thomas > >> +} >> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed); >> diff --git a/include/drm/drm_format_helper.h >> b/include/drm/drm_format_helper.h >> index b30ed5de0a33..85e551a5cbe6 100644 >> --- a/include/drm/drm_format_helper.h >> +++ b/include/drm/drm_format_helper.h >> @@ -43,4 +43,11 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned >> int dst_pitch, uint32_t dst_for >> const void *vmap, const struct drm_framebuffer *fb, >> const struct drm_rect *rect); >> +void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, >> const void *src, >> + const struct drm_rect *clip); >> + >> +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int >> dst_pitch, const void *src, >> + const struct drm_framebuffer *fb, >> + const struct drm_rect *clip); >> + >> #endif /* __LINUX_DRM_FORMAT_HELPER_H */ >
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev [unhandled content-type:application/pgp-signature]
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