[PATCH libdrm 3/3] util: Add SMPTE pattern support for C4 format

[Geert Uytterhoeven]

Add support for drawing the SMPTE pattern in a buffer using the C4
indexed format.

Note that this still uses 256 instead of 16 as the CLUT size, as
DRM_IOCTL_MODE_SETGAMMA enforces that the size matches against the
(fixed) gamma size, while the CLUT size depends on the format.

Signed-off-by: Geert Uytterhoeven <geert at linux-m68k.org>
---
The linuxdoc comments say userspace can query the gamma size:

 * drm_mode_gamma_set_ioctl - set the gamma table
 *
 * Set the gamma table of a CRTC to the one passed in by the user. Userspace can
 * inquire the required gamma table size through drm_mode_gamma_get_ioctl.

 * drm_mode_gamma_get_ioctl - get the gamma table
 *
 * Copy the current gamma table into the storage provided. This also provides
 * the gamma table size the driver expects, which can be used to size the
 * allocated storage.

but the code doesn't seem to support that in an easy way (like setting
red/green/blue to NULL on input, retrieving gamma_size on output), only
by providing big enough buffers for red/green/blue, and looping over
gamma_size until -EINVAL is no longer returned.
---
 tests/modetest/modetest.c | 11 +++++++---
 tests/util/pattern.c      | 42 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/tests/modetest/modetest.c b/tests/modetest/modetest.c
index e369044fb7a484c1..205b7093b0045e01 100644
--- a/tests/modetest/modetest.c
+++ b/tests/modetest/modetest.c
@@ -1122,16 +1122,21 @@ static void set_gamma(struct device *dev, unsigned crtc_id, unsigned fourcc)
 	struct drm_color_lut gamma_lut[256];
 	int i, ret;
 
-	if (fourcc == DRM_FORMAT_C8) {
-		/* TODO: Add C8 support for more patterns */
+	switch (fourcc) {
+	case DRM_FORMAT_C4:
+	case DRM_FORMAT_C8:
+		/* TODO: Add index support for more patterns */
 		util_smpte_index_gamma(256, gamma_lut);
 		drmModeCreatePropertyBlob(dev->fd, gamma_lut, sizeof(gamma_lut), &blob_id);
-	} else {
+		break;
+
+	default:
 		for (i = 0; i < 256; i++) {
 			gamma_lut[i].red =
 			gamma_lut[i].green =
 			gamma_lut[i].blue = i << 8;
 		}
+		break;
 	}
 
 	add_property_optional(dev, crtc_id, "DEGAMMA_LUT", 0);
diff --git a/tests/util/pattern.c b/tests/util/pattern.c
index 953bf95492ee150c..42d75d700700dc3d 100644
--- a/tests/util/pattern.c
+++ b/tests/util/pattern.c
@@ -608,6 +608,46 @@ static void fill_smpte_rgb16fp(const struct util_rgb_info *rgb, void *mem,
 static unsigned int smpte_middle[7] = { 6, 7, 4, 7, 2, 7, 0 };
 static unsigned int smpte_bottom[8] = { 8, 9, 10, 7, 11, 7, 12, 7 };
 
+static void write_pixel_4(uint8_t *mem, unsigned int x, unsigned int pixel)
+{
+	if (x & 1)
+		mem[x / 2] = (mem[x / 2] & 0xf0) | (pixel & 0x0f);
+	else
+		mem[x / 2] = (mem[x / 2] & 0x0f) | (pixel << 4);
+}
+
+static void fill_smpte_c4(void *mem, unsigned int width, unsigned int height,
+			  unsigned int stride)
+{
+	unsigned int x;
+	unsigned int y;
+
+	for (y = 0; y < height * 6 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_pixel_4(mem, x, x * 7 / width);
+		mem += stride;
+	}
+
+	for (; y < height * 7 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_pixel_4(mem, x, smpte_middle[x * 7 / width]);
+		mem += stride;
+	}
+
+	for (; y < height; ++y) {
+		for (x = 0; x < width * 5 / 7; ++x)
+			write_pixel_4(mem, x,
+				      smpte_bottom[x * 4 / (width * 5 / 7)]);
+		for (; x < width * 6 / 7; ++x)
+			write_pixel_4(mem, x,
+				      smpte_bottom[(x - width * 5 / 7) * 3 /
+						   (width / 7) + 4]);
+		for (; x < width; ++x)
+			write_pixel_4(mem, x, smpte_bottom[7]);
+		mem += stride;
+	}
+}
+
 static void fill_smpte_c8(void *mem, unsigned int width, unsigned int height,
 			  unsigned int stride)
 {
@@ -688,6 +728,8 @@ static void fill_smpte(const struct util_format_info *info, void *planes[3],
 	unsigned char *u, *v;
 
 	switch (info->format) {
+	case DRM_FORMAT_C4:
+		return fill_smpte_c4(planes[0], width, height, stride);
 	case DRM_FORMAT_C8:
 		return fill_smpte_c8(planes[0], width, height, stride);
 	case DRM_FORMAT_UYVY:
-- 
2.25.1