[PATCH 4/5] drm/format-helper: introduce drm_fb_xrgb8888_to_gray2()
Thomas Zimmermann
tzimmermann at suse.de
Mon Jul 14 09:13:04 UTC 2025
Hi
Am 14.07.25 um 10:04 schrieb Marcus Folkesson:
> drm_fb_xrgb8888_to_gray2() works like and share much code with
> drm_fb_xrgb8888_to_mono(), but converts XRGB8888 to
> 2bit grayscale instead.
>
> It uses drm_fb_xrgb8888_to_gray8() to convert the pixels to gray8 as an
> intermediate step before converting to gray2.
Please don't share code here. This needs a serious rework anyway. The
best thing for now is to add a new, separate function for _gray2().
Best regards
Thomas
>
> Signed-off-by: Marcus Folkesson <marcus.folkesson at gmail.com>
> ---
> drivers/gpu/drm/drm_format_helper.c | 148 ++++++++++++++++++++++++++----------
> include/drm/drm_format_helper.h | 4 +
> 2 files changed, 110 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> index 8f3daf38ca639d3d39742c2c9fa0c54a3a9297a5..2f2171b3df609263cc9ce6809bf6144028c25380 100644
> --- a/drivers/gpu/drm/drm_format_helper.c
> +++ b/drivers/gpu/drm/drm_format_helper.c
> @@ -1253,6 +1253,25 @@ int drm_fb_blit(struct iosys_map *dst, const unsigned int *dst_pitch, uint32_t d
> }
> EXPORT_SYMBOL(drm_fb_blit);
>
> +static void drm_fb_gray8_to_gray2_line(void *dbuf, const void *sbuf, unsigned int pixels)
> +{
> + u8 *dbuf8 = dbuf;
> + const u8 *sbuf8 = sbuf;
> + u8 px;
> +
> + while (pixels) {
> + unsigned int i, bits = min(pixels, 4U);
> + u8 byte = 0;
> +
> + for (i = 0; i < bits; i++, pixels--) {
> + byte >>= 2;
> + px = (*sbuf8++ * 3 + 127) / 255;
> + byte |= (px &= 0x03) << 6;
> + }
> + *dbuf8++ = byte;
> + }
> +}
> +
> static void drm_fb_gray8_to_mono_line(void *dbuf, const void *sbuf, unsigned int pixels)
> {
> u8 *dbuf8 = dbuf;
> @@ -1270,40 +1289,11 @@ static void drm_fb_gray8_to_mono_line(void *dbuf, const void *sbuf, unsigned int
> }
> }
>
> -/**
> - * drm_fb_xrgb8888_to_mono - Convert XRGB8888 to monochrome
> - * @dst: Array of monochrome destination buffers (0=black, 1=white)
> - * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
> - * within @dst; can be NULL if scanlines are stored next to each other.
> - * @src: Array of XRGB8888 source buffers
> - * @fb: DRM framebuffer
> - * @clip: Clip rectangle area to copy
> - * @state: Transform and conversion state
> - *
> - * This function copies parts of a framebuffer to display memory and converts the
> - * color format during the process. Destination and framebuffer formats must match. The
> - * parameters @dst, @dst_pitch and @src refer to arrays. Each array must have at
> - * least as many entries as there are planes in @fb's format. Each entry stores the
> - * value for the format's respective color plane at the same index.
> - *
> - * This function does not apply clipping on @dst (i.e. the destination is at the
> - * top-left corner). The first pixel (upper left corner of the clip rectangle) will
> - * be converted and copied to the first bit (LSB) in the first byte of the monochrome
> - * destination buffer. If the caller requires that the first pixel in a byte must
> - * be located at an x-coordinate that is a multiple of 8, then the caller must take
> - * care itself of supplying a suitable clip rectangle.
> - *
> - * DRM doesn't have native monochrome support. Drivers can use this function for
> - * monochrome devices that don't support XRGB8888 natively. 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 monochrome.
> - */
> -void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitch,
> - const struct iosys_map *src, const struct drm_framebuffer *fb,
> - const struct drm_rect *clip, struct drm_format_conv_state *state)
> +static void drm_fb_xrgb8888_to_gray(u8 *dst, const unsigned int *dst_pitch,
> + u8 *src, const struct drm_framebuffer *fb,
> + const struct drm_rect *clip, struct drm_format_conv_state *state,
> + u8 bpp,
> + void (*xfrm_line)(void *dbuf, const void *sbuf, unsigned int npixels))
> {
> static const unsigned int default_dst_pitch[DRM_FORMAT_MAX_PLANES] = {
> 0, 0, 0, 0
> @@ -1313,11 +1303,10 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc
> unsigned int cpp = fb->format->cpp[0];
> unsigned int len_src32 = linepixels * cpp;
> struct drm_device *dev = fb->dev;
> - void *vaddr = src[0].vaddr;
> unsigned int dst_pitch_0;
> unsigned int y;
> - u8 *mono = dst[0].vaddr, *gray8;
> u32 *src32;
> + u8 *gray8;
>
> if (drm_WARN_ON(dev, fb->format->format != DRM_FORMAT_XRGB8888))
> return;
> @@ -1330,7 +1319,7 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc
> * The mono destination buffer contains 1 bit per pixel
> */
> if (!dst_pitch_0)
> - dst_pitch_0 = DIV_ROUND_UP(linepixels, 8);
> + dst_pitch_0 = DIV_ROUND_UP(linepixels, 8 / bpp);
>
> /*
> * The dma memory is write-combined so reads are uncached.
> @@ -1349,13 +1338,88 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc
>
> gray8 = (u8 *)src32 + len_src32;
>
> - vaddr += clip_offset(clip, fb->pitches[0], cpp);
> + src += clip_offset(clip, fb->pitches[0], cpp);
> for (y = 0; y < lines; y++) {
> - src32 = memcpy(src32, vaddr, len_src32);
> + src32 = memcpy(src32, src, len_src32);
> drm_fb_xrgb8888_to_gray8_line(gray8, src32, linepixels);
> - drm_fb_gray8_to_mono_line(mono, gray8, linepixels);
> - vaddr += fb->pitches[0];
> - mono += dst_pitch_0;
> + xfrm_line(dst, gray8, linepixels);
> + src += fb->pitches[0];
> + dst += dst_pitch_0;
> }
> }
> +
> +/**
> + * drm_fb_xrgb8888_to_mono - Convert XRGB8888 to monochrome
> + * @dst: Array of monochrome destination buffers (0=black, 1=white)
> + * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
> + * within @dst; can be NULL if scanlines are stored next to each other.
> + * @src: Array of XRGB8888 source buffers
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + * @state: Transform and conversion state
> + *
> + * DRM doesn't have native monochrome support. Drivers can use this function for
> + * monochrome devices that don't support XRGB8888 natively. Such drivers can
> + * announce the commonly supported XR24 format to userspace and use this function
> + * to convert to the native format.
> + *
> + * This function copies parts of a framebuffer to display memory and converts the
> + * color format during the process. Destination and framebuffer formats must match. The
> + * parameters @dst, @dst_pitch and @src refer to arrays. Each array must have at
> + * least as many entries as there are planes in @fb's format. Each entry stores the
> + * value for the format's respective color plane at the same index.
> + *
> + * This function does not apply clipping on @dst (i.e. the destination is at the
> + * top-left corner). The first pixel (upper left corner of the clip rectangle) will
> + * be converted and copied to the first bit (LSB) in the first byte of the monochrome
> + * destination buffer. If the caller requires that the first pixel in a byte must
> + * be located at an x-coordinate that is a multiple of 8, then the caller must take
> + * care itself of supplying a suitable clip rectangle.
> + *
> + *
> + * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and
> + * then the result is converted from grayscale to monochrome.
> + */
> +
> +
> +void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitch,
> + const struct iosys_map *src, const struct drm_framebuffer *fb,
> + const struct drm_rect *clip, struct drm_format_conv_state *state)
> +{
> + drm_fb_xrgb8888_to_gray(dst[0].vaddr, dst_pitch, src[0].vaddr, fb, clip, state,
> + 1, drm_fb_gray8_to_mono_line);
> +}
> EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono);
> +
> +/**
> + * drm_fb_xrgb8888_to_gray2 - Convert XRGB8888 to gray2
> + * @dst: Array of gray2 destination buffers
> + * @dst_pitch: Array of numbers of bytes between the start of two consecutive scanlines
> + * within @dst; can be NULL if scanlines are stored next to each other.
> + * @src: Array of XRGB8888 source buffers
> + * @fb: DRM framebuffer
> + * @clip: Clip rectangle area to copy
> + * @state: Transform and conversion state
> + *
> + * This function copies parts of a framebuffer to display memory and converts the
> + * color format during the process. Destination and framebuffer formats must match. The
> + * parameters @dst, @dst_pitch and @src refer to arrays. Each array must have at
> + * least as many entries as there are planes in @fb's format. Each entry stores the
> + * value for the format's respective color plane at the same index.
> + *
> + * DRM doesn't have native gray2 support. Drivers can use this function for
> + * gray2 devices that don't support XRGB8888 natively. 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 gray2.
> + */
> +void drm_fb_xrgb8888_to_gray2(struct iosys_map *dst, const unsigned int *dst_pitch,
> + const struct iosys_map *src, const struct drm_framebuffer *fb,
> + const struct drm_rect *clip, struct drm_format_conv_state *state)
> +{
> + drm_fb_xrgb8888_to_gray(dst[0].vaddr, dst_pitch, src[0].vaddr, fb, clip, state,
> + 2, drm_fb_gray8_to_gray2_line);
> +}
> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_gray2);
> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> index 562bc383ece4e90d96aa92b47b4f69609f825a6e..8488befafb7e0e0311f87bd2fef5011bab45065b 100644
> --- a/include/drm/drm_format_helper.h
> +++ b/include/drm/drm_format_helper.h
> @@ -136,4 +136,8 @@ void drm_fb_xrgb8888_to_mono(struct iosys_map *dst, const unsigned int *dst_pitc
> const struct iosys_map *src, const struct drm_framebuffer *fb,
> const struct drm_rect *clip, struct drm_format_conv_state *state);
>
> +void drm_fb_xrgb8888_to_gray2(struct iosys_map *dst, const unsigned int *dst_pitch,
> + const struct iosys_map *src, const struct drm_framebuffer *fb,
> + const struct drm_rect *clip, struct drm_format_conv_state *state);
> +
> #endif /* __LINUX_DRM_FORMAT_HELPER_H */
>
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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