Re: [PATCH v4 2/6] drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed()

Hi

Am 11.02.22 um 10:19 schrieb Javier Martinez Canillas:

Add support to convert from XR24 to reversed monochrome for drivers that control monochromatic display panels, that only have 1 bit per pixel.

The function does a line-by-line conversion doing an intermediate step first from XR24 to 8-bit grayscale and then to reversed monochrome.

The drm_fb_gray8_to_mono_reversed_line() helper was based on code from drivers/gpu/drm/tiny/repaper.c driver.

Signed-off-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Thomas Zimmermann tzimmermann@suse.de

---

Changes in v4:

• Rename end_offset to end_len (Thomas Zimmermann)
• Warn once if dst_pitch is not a multiple of 8 (Thomas Zimmermann)
• Drop drm_fb_gray8_to_mono_reversed() that's not used (Thomas Zimmermann)
• Allocate single buffer for both copy cma memory and gray8 (Thomas Zimmermann)
• Add Thomas Zimmermann Reviewed-by tag to patch adding XR24 -> mono helper.

Changes in v3:

• Also add a drm_fb_xrgb8888_to_mono_reversed() helper (Thomas Zimmermann)

• Split lines copy to drm_fb_gray8_to_mono_reversed_line() (Thomas Zimmermann)

• Handle case where the source buffer is not aligned to 8 (Thomas Zimmermann)

  drivers/gpu/drm/drm_format_helper.c | 107 ++++++++++++++++++++++++++++ include/drm/drm_format_helper.h | 4 ++ 2 files changed, 111 insertions(+)

diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c index b981712623d3..ec4e3724ee79 100644 --- a/drivers/gpu/drm/drm_format_helper.c +++ b/drivers/gpu/drm/drm_format_helper.c @@ -591,3 +591,110 @@ 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, unsigned int pixels,

• 			       unsigned int start_offset, unsigned int end_len)
  

+{

• unsigned int xb, i;
• for (xb = 0; xb < pixels; xb++) {

• unsigned int start = 0, end = 8;
  

• u8 byte = 0x00;
  

• if (xb == 0 && start_offset)
  

• 	start = start_offset;
  

• if (xb == pixels - 1 && end_len)
  

• 	end = end_len;
  

• for (i = start; i < end; i++) {
  

• 	unsigned int x = xb * 8 + i;
  

• 	byte >>= 1;
  

• 	if (src[x] >> 7)
  

• 		byte |= BIT(7);
  

• }
  

• *dst++ = byte;
  

• }

+}

+/**

• • 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 *vaddr,

• 		      const struct drm_framebuffer *fb, const struct drm_rect *clip)
  

+{

• unsigned int linepixels = drm_rect_width(clip);
• unsigned int lines = clip->y2 - clip->y1;
• unsigned int cpp = fb->format->cpp[0];
• unsigned int len_src32 = linepixels * cpp;
• unsigned int start_offset, end_len;
• unsigned int y;
• u8 *mono = dst, *gray8;
• u32 *src32;
• if (WARN_ON(fb->format->format != DRM_FORMAT_XRGB8888))

• return;
  

These WARN macros are deprecated. Use drm_warn, drm_WARN_ONCE, etc instead.

Best regards Thomas

• /*

• * The reversed mono destination buffer contains 1 bit per pixel
  

• * and destination scanlines have to be in multiple of 8 pixels.
  

• */
  

• if (!dst_pitch)

• dst_pitch = DIV_ROUND_UP(linepixels, 8);
  

• WARN_ONCE(dst_pitch % 8 != 0, "dst_pitch is not a multiple of 8\n");
• /*

• * The cma memory is write-combined so reads are uncached.
  

• * Speed up by fetching one line at a time.
  

• *
  

• * Also, format conversion from XR24 to reversed monochrome
  

• * are done line-by-line but are converted to 8-bit grayscale
  

• * as an intermediate step.
  

• *
  

• * Allocate a buffer to be used for both copying from the cma
  

• * memory and to store the intermediate grayscale line pixels.
  

• */
  

• src32 = kmalloc(len_src32 + linepixels, GFP_KERNEL);
• if (!src32)

• return;
  

• gray8 = (u8 *)src32 + len_src32;
• /*

• * For damage handling, it is possible that only parts of the source
  

• * buffer is copied and this could lead to start and end pixels that
  

• * are not aligned to multiple of 8.
  

• *
  

• * Calculate if the start and end pixels are not aligned and set the
  

• * offsets for the reversed mono line conversion function to adjust.
  

• */
  

• start_offset = clip->x1 % 8;
• end_len = clip->x2 % 8;
• vaddr += clip_offset(clip, fb->pitches[0], cpp);
• for (y = 0; y < lines; y++) {

• src32 = memcpy(src32, vaddr, len_src32);
  

• drm_fb_xrgb8888_to_gray8_line(gray8, src32, linepixels);
  

• drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch,
  

• 				   start_offset, end_len);
  

• vaddr += fb->pitches[0];
  

• mono += dst_pitch;
  

• }
• kfree(src32);

+} +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..0b0937c0b2f6 100644 --- a/include/drm/drm_format_helper.h +++ b/include/drm/drm_format_helper.h @@ -43,4 +43,8 @@ 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_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 */