media: tc358743: Fix the RGB MBUS format

Upstream series https://lore.kernel.org/linux-media/20250917-csi-bgr-rgb-v3-0-0145571b3aa4@kernel.org/

The tc358743 is an HDMI to MIPI-CSI2 bridge. It can output all three
HDMI 1.4 video formats: RGB 4:4:4, YCbCr 4:2:2, and YCbCr 4:4:4.

RGB 4:4:4 is converted to the MIPI-CSI2 RGB888 video format, and listed
in the driver as MEDIA_BUS_FMT_RGB888_1X24.

Most CSI2 receiver drivers then map MEDIA_BUS_FMT_RGB888_1X24 to
V4L2_PIX_FMT_RGB24.

However, V4L2_PIX_FMT_RGB24 is defined as having its color components in
the R, G and B order, from left to right. MIPI-CSI2 however defines the
RGB888 format with blue first.

This essentially means that the R and B will be swapped compared to what
V4L2_PIX_FMT_RGB24 defines.

The proper MBUS format would be BGR888, so let's use that.

Fixes: d32d986 ("[media] Driver for Toshiba TC358743 HDMI to CSI-2 bridge")
Signed-off-by: Maxime Ripard <mripard@kernel.org>

Author: mripard

drivers/media/i2c/tc358743.c

@@ -756,6 +756,7 @@ static void tc358743_set_ref_clk(struct v4l2_subdev *sd)
 static void tc358743_set_csi_color_space(struct v4l2_subdev *sd)
 {
 	struct tc358743_state *state = to_state(sd);
+	struct device *dev = &state->i2c_client->dev;
 
 	switch (state->mbus_fmt_code) {
 	case MEDIA_BUS_FMT_UYVY8_1X16:
@@ -771,7 +772,17 @@ static void tc358743_set_csi_color_space(struct v4l2_subdev *sd)
 		mutex_unlock(&state->confctl_mutex);
 		break;
 	case MEDIA_BUS_FMT_RGB888_1X24:
-		v4l2_dbg(2, debug, sd, "%s: RGB 888 24-bit\n", __func__);
+		/*
+		 * The driver was initially introduced with RGB888
+		 * support, but CSI really means BGR.
+		 *
+		 * Since we might have applications that would have
+		 * hard-coded the RGB888, let's support both.
+		 */
+		dev_warn_once(dev, "RGB format isn't actually supported by the hardware. The application should be fixed to use BGR.");
+		fallthrough;
+	case MEDIA_BUS_FMT_BGR888_1X24:
+		v4l2_dbg(2, debug, sd, "%s: BGR 888 24-bit\n", __func__);
 		i2c_wr8_and_or(sd, VOUT_SET2,
 				~(MASK_SEL422 | MASK_VOUT_422FIL_100) & 0xff,
 				0x00);
@@ -1432,11 +1443,26 @@ static int tc358743_log_status(struct v4l2_subdev *sd)
 	v4l2_info(sd, "Stopped: %s\n",
 			(i2c_rd16(sd, CSI_STATUS) & MASK_S_HLT) ?
 			"yes" : "no");
-	v4l2_info(sd, "Color space: %s\n",
-			state->mbus_fmt_code == MEDIA_BUS_FMT_UYVY8_1X16 ?
-			"YCbCr 422 16-bit" :
-			state->mbus_fmt_code == MEDIA_BUS_FMT_RGB888_1X24 ?
-			"RGB 888 24-bit" : "Unsupported");
+
+	switch (state->mbus_fmt_code) {
+	case MEDIA_BUS_FMT_BGR888_1X24:
+		/*
+		 * The driver was initially introduced with RGB888
+		 * support, but CSI really means BGR.
+		 *
+		 * Since we might have applications that would have
+		 * hard-coded the RGB888, let's support both.
+		 */
+	case MEDIA_BUS_FMT_RGB888_1X24:
+		v4l2_info(sd, "Color space: BGR 888 24-bit\n");
+		break;
+	case MEDIA_BUS_FMT_UYVY8_1X16:
+		v4l2_info(sd, "Color space: YCbCr 422 16-bit\n");
+		break;
+	default:
+		v4l2_info(sd, "Color space: Unsupported\n");
+		break;
+	}
 
 	v4l2_info(sd, "-----%s status-----\n", is_hdmi(sd) ? "HDMI" : "DVI-D");
 	v4l2_info(sd, "HDCP encrypted content: %s\n",
@@ -1773,11 +1799,18 @@ static int tc358743_enum_mbus_code(struct v4l2_subdev *sd,
 {
 	switch (code->index) {
 	case 0:
-		code->code = MEDIA_BUS_FMT_RGB888_1X24;
+		code->code = MEDIA_BUS_FMT_BGR888_1X24;
 		break;
 	case 1:
 		code->code = MEDIA_BUS_FMT_UYVY8_1X16;
 		break;
+	case 2:
+		/*
+		 * We need to keep RGB888 for backward compatibility,
+		 * but we should list it last for userspace to pick BGR.
+		 */
+		code->code = MEDIA_BUS_FMT_RGB888_1X24;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -1787,6 +1820,7 @@ static int tc358743_enum_mbus_code(struct v4l2_subdev *sd,
 static u32 tc358743_g_colorspace(u32 code)
 {
 	switch (code) {
+	case MEDIA_BUS_FMT_BGR888_1X24:
 	case MEDIA_BUS_FMT_RGB888_1X24:
 		return V4L2_COLORSPACE_SRGB;
 	case MEDIA_BUS_FMT_UYVY8_1X16:
@@ -1824,7 +1858,8 @@ static int tc358743_set_fmt(struct v4l2_subdev *sd,
 	u32 code = format->format.code; /* is overwritten by get_fmt */
 	int ret = tc358743_get_fmt(sd, sd_state, format);
 
-	if (code == MEDIA_BUS_FMT_RGB888_1X24 ||
+	if (code == MEDIA_BUS_FMT_BGR888_1X24 ||
+	    code == MEDIA_BUS_FMT_RGB888_1X24 ||
 	    code == MEDIA_BUS_FMT_UYVY8_1X16)
 		format->format.code = code;
 	format->format.colorspace = tc358743_g_colorspace(format->format.code);
@@ -2244,7 +2279,7 @@ static int tc358743_probe(struct i2c_client *client)
 	if (err < 0)
 		goto err_hdl;
 
-	state->mbus_fmt_code = MEDIA_BUS_FMT_RGB888_1X24;
+	state->mbus_fmt_code = MEDIA_BUS_FMT_BGR888_1X24;
 
 	sd->dev = &client->dev;