modetest: add SMPTE pattern support for C[124] formats

Add support for drawing the SMPTE pattern in buffers using a
color-indexed frame buffer formats with two, four, or sixteen colors.

Note that this still uses 256 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.

Move clearing the color LUT entries from util_smpte_index_gamma() to its
caller, as only the caller knows how many entries there really are
(currently DRM always assumes 256 entries).

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
v5:
  - Add Reviewed-by,

v4:
  - Add missing C[12] to oneline-summary,
  - Do not remove memset() of full lut, else some entries may stay
    uninitialized,

v3:
  - Add Acked-by,

v2:
  - Split off changes to tests/modetest/modetest.c,
  - Add C1 and C2 support.

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.

1 files changed, 6 insertions, 3 deletions

diff --git a/tests/modetest/modetest.c b/tests/modetest/modetest.c
index 9504fbd8..9b1aa537 100644
--- a/tests/modetest/modetest.c
+++ b/tests/modetest/modetest.c
@@ -1149,13 +1149,16 @@ static bool add_property_optional(struct device *dev, uint32_t obj_id,
 static void set_gamma(struct device *dev, unsigned crtc_id, unsigned fourcc)
 {
 	unsigned blob_id = 0;
+	const struct util_format_info *info;
 	/* TODO: support 1024-sized LUTs, when the use-case arises */
 	struct drm_color_lut gamma_lut[256];
 	int i, ret;
 
-	if (fourcc == DRM_FORMAT_C8) {
-		/* TODO: Add C8 support for more patterns */
-		util_smpte_fill_lut(256, gamma_lut);
+	info = util_format_info_find(fourcc);
+	if (info->ncolors) {
+		memset(gamma_lut, 0, sizeof(gamma_lut));
+		/* TODO: Add index support for more patterns */
+		util_smpte_fill_lut(info->ncolors, gamma_lut);
 		drmModeCreatePropertyBlob(dev->fd, gamma_lut, sizeof(gamma_lut), &blob_id);
 	} else {
 		/*