drm/gud: Add GUD_PIXEL_FORMAT_R8

Add support for 8-bit greyscale format.
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210929191201.34456-5-noralf@tronnes.org

drivers/gpu/drm/gud/gud_drv.c

@@ -523,6 +523,8 @@ static int gud_probe(struct usb_interface *intf, const struct usb_device_id *id)
 		switch (format) {
 		case GUD_DRM_FORMAT_R1:
 			fallthrough;
+		case DRM_FORMAT_R8:
+			fallthrough;
 		case GUD_DRM_FORMAT_XRGB1111:
 			if (!xrgb8888_emulation_format)
 				xrgb8888_emulation_format = info;

drivers/gpu/drm/gud/gud_internal.h

@@ -80,6 +80,8 @@ static inline u8 gud_from_fourcc(u32 fourcc)
 	switch (fourcc) {
 	case GUD_DRM_FORMAT_R1:
 		return GUD_PIXEL_FORMAT_R1;
+	case DRM_FORMAT_R8:
+		return GUD_PIXEL_FORMAT_R8;
 	case GUD_DRM_FORMAT_XRGB1111:
 		return GUD_PIXEL_FORMAT_XRGB1111;
 	case DRM_FORMAT_RGB565:
@@ -98,6 +100,8 @@ static inline u32 gud_to_fourcc(u8 format)
 	switch (format) {
 	case GUD_PIXEL_FORMAT_R1:
 		return GUD_DRM_FORMAT_R1;
+	case GUD_PIXEL_FORMAT_R8:
+		return DRM_FORMAT_R8;
 	case GUD_PIXEL_FORMAT_XRGB1111:
 		return GUD_DRM_FORMAT_XRGB1111;
 	case GUD_PIXEL_FORMAT_RGB565:

drivers/gpu/drm/gud/gud_pipe.c

@@ -189,6 +189,8 @@ static int gud_prep_flush(struct gud_device *gdrm, struct drm_framebuffer *fb,
 				ret = -ENOMEM;
 				goto end_cpu_access;
 			}
+		} else if (format->format == DRM_FORMAT_R8) {
+			drm_fb_xrgb8888_to_gray8(buf, vaddr, fb, rect);
 		} else if (format->format == DRM_FORMAT_RGB565) {
 			drm_fb_xrgb8888_to_rgb565(buf, vaddr, fb, rect, gud_is_big_endian());
 		} else {

include/drm/gud.h

@@ -246,8 +246,8 @@ struct gud_state_req {
 /* Get supported pixel formats as a byte array of GUD_PIXEL_FORMAT_* */
 #define GUD_REQ_GET_FORMATS				0x40
   #define GUD_FORMATS_MAX_NUM			32
-  /* R1 is a 1-bit monochrome transfer format presented to userspace as XRGB8888 */
-  #define GUD_PIXEL_FORMAT_R1			0x01
+  #define GUD_PIXEL_FORMAT_R1			0x01 /* 1-bit monochrome */
+  #define GUD_PIXEL_FORMAT_R8			0x08 /* 8-bit greyscale */
   #define GUD_PIXEL_FORMAT_XRGB1111		0x20
   #define GUD_PIXEL_FORMAT_RGB565		0x40
   #define GUD_PIXEL_FORMAT_XRGB8888		0x80