drm/format-helper: Rename drm_fb_xrgb8888_to_mono_reversed()

There is no "reversed" handling in drm_fb_xrgb8888_to_mono_reversed():
the function just converts from color to grayscale, and reduces the
number of grayscale levels from 256 to 2 (i.e. brightness 0-127 is
mapped to 0, 128-255 to 1).  All "reversed" handling is done in the
repaper driver, where this function originated.

Hence make this clear by renaming drm_fb_xrgb8888_to_mono_reversed() to
drm_fb_xrgb8888_to_mono(), and documenting the black/white pixel
mapping.

Fixes: bcf8b616 ("drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed()")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220317081830.1211400-2-geert@linux-m68k.org

drivers/gpu/drm/drm_format_helper.c

@@ -594,8 +594,8 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for
 }
 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)
+static void drm_fb_gray8_to_mono_line(u8 *dst, const u8 *src, unsigned int pixels,
+				      unsigned int start_offset, unsigned int end_len)
 {
 	unsigned int xb, i;
 
@@ -621,8 +621,8 @@ static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, unsigned
 }
 
 /**
- * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome
- * @dst: reversed monochrome destination buffer
+ * drm_fb_xrgb8888_to_mono - Convert XRGB8888 to monochrome
+ * @dst: monochrome destination buffer (0=black, 1=white)
  * @dst_pitch: Number of bytes between two consecutive scanlines within dst
  * @src: XRGB8888 source buffer
  * @fb: DRM framebuffer
@@ -633,10 +633,10 @@ static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, unsigned
  * 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.
+ * then the result is converted from grayscale to monochrome.
  */
-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)
+void drm_fb_xrgb8888_to_mono(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;
@@ -652,8 +652,8 @@ void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const v
 		return;
 
 	/*
-	 * The reversed mono destination buffer contains 1 bit per pixel
-	 * and destination scanlines have to be in multiple of 8 pixels.
+	 * The 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);
@@ -664,9 +664,9 @@ void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const v
 	 * 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.
+	 * Also, format conversion from XR24 to 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.
@@ -683,7 +683,7 @@ void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const v
 	 * 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.
+	 * offsets for the mono line conversion function to adjust.
 	 */
 	start_offset = clip->x1 % 8;
 	end_len = clip->x2 % 8;
@@ -692,12 +692,11 @@ void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const v
 	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);
+		drm_fb_gray8_to_mono_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);
+EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono);

drivers/gpu/drm/solomon/ssd130x.c

@@ -458,7 +458,7 @@ static int ssd130x_fb_blit_rect(struct drm_framebuffer *fb, const struct dma_buf
 	if (!buf)
 		return -ENOMEM;
 
-	drm_fb_xrgb8888_to_mono_reversed(buf, 0, vmap, fb, rect);
+	drm_fb_xrgb8888_to_mono(buf, 0, vmap, fb, rect);
 
 	ssd130x_update_rect(ssd130x, buf, rect);
 

drivers/gpu/drm/tiny/repaper.c

@@ -540,7 +540,7 @@ static int repaper_fb_dirty(struct drm_framebuffer *fb)
 	if (ret)
 		goto out_free;
 
-	drm_fb_xrgb8888_to_mono_reversed(buf, 0, cma_obj->vaddr, fb, &clip);
+	drm_fb_xrgb8888_to_mono(buf, 0, cma_obj->vaddr, fb, &clip);
 
 	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 

include/drm/drm_format_helper.h

@@ -43,8 +43,7 @@ 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);
+void drm_fb_xrgb8888_to_mono(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 */