Messages in this thread Patch in this message | | | Date | Fri, 4 Feb 2022 16:52:54 +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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Hi
Am 04.02.22 um 14:43 schrieb Javier Martinez Canillas: > Add support to convert XR24 and 8-bit grayscale to reversed monochrome for > drivers that control monochromatic panels, that only have 1 bit per pixel. > > The drm_fb_gray8_to_mono_reversed() helper was based on the function that > does the same in the drivers/gpu/drm/tiny/repaper.c driver. > > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> > --- > > (no changes since v1) > > drivers/gpu/drm/drm_format_helper.c | 80 +++++++++++++++++++++++++++++ > include/drm/drm_format_helper.h | 7 +++ > 2 files changed, 87 insertions(+) > > diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c > index 0f28dd2bdd72..cdce4b7c25d9 100644 > --- a/drivers/gpu/drm/drm_format_helper.c > +++ b/drivers/gpu/drm/drm_format_helper.c > @@ -584,3 +584,83 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for > return -EINVAL; > } > EXPORT_SYMBOL(drm_fb_blit_toio); > + > +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, size_t pixels) > +{ > + unsigned int xb, i; > + > + for (xb = 0; xb < pixels / 8; xb++) {
In practice, all mode widths are multiples of 8 because VGA mandated it. So it's ok-ish to assume this here. You should probably at least print a warning somewhere if (pixels % 8 != 0)
> + u8 byte = 0x00; > + > + for (i = 0; i < 8; i++) { > + int x = xb * 8 + i; > + > + byte >>= 1; > + if (src[x] >> 7) > + byte |= BIT(7); > + } > + *dst++ = byte; > + } > +} > + > +/** > + * drm_fb_gray8_to_mono_reversed - Convert grayscale to reversed monochrome > + * @dst: reversed monochrome destination buffer > + * @dst_pitch: Number of bytes between two consecutive scanlines within dst > + * @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, unsigned int dst_pitch, const void *src, > + const struct drm_rect *clip)
There's a bug here. You want to pass in a drm_framebuffer as fourth argument.
> +{ > + > + size_t height = drm_rect_height(clip); > + size_t width = drm_rect_width(clip); > + unsigned int y; > + const u8 *gray8 = src; > + u8 *mono = dst; > + > + if (!dst_pitch) > + dst_pitch = width;
The dst_pitch is given in bytes. You have to device by 8. Here would be a good place to warn if (width % 8 != 0).
> + > + for (y = 0; y < height; y++) { > + drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch); > + mono += (dst_pitch / 8);
The dst_pitch is already given in bytes.
> + gray8 += dst_pitch;
'gray8 += fb->pitches[0]' would be correct.
> + } > +} > + > +/** > + * 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, ...);
src += fb->pitches[0] dst += dst_pitch; }
kfree(tmp); }
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] | |