From: Maxime Ripard <mripard@redhat.com>

The Unicam driver is a MIPI-CSI2 Receiver, that can capture RGB 4:4:4,
YCbCr 4:2:2, and raw formats.

RGB 4:4:4 is converted to the MIPI-CSI2 RGB888 video format, and
associated to the MEDIA_BUS_FMT_RGB888_1X24 media bus code.

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, and that's what MEDIA_BUS_FMT_RGB888_1X24
defines too.

This essentially means that the R and B will be swapped compared to what
V4L2_PIX_FMT_RGB24 defines. The same situation occurs with
V4L2_PIX_FMT_BGR24 being associated to MEDIA_BUS_FMT_BGR888_1X24.

In order to fix the swapped components, we need to change the
association of V4L2_PIX_FMT_BGR24 to MEDIA_BUS_FMT_RGB888_1X24, and of
V4L2_PIX_FMT_RGB24 to MEDIA_BUS_FMT_BGR888_1X24.

Since the media bus code is exposed to userspace, and validated by
unicam's link_validate implementation, we need to explicitly accept (and
warn) the old association still to preserve backward compatibility.

Signed-off-by: Maxime Ripard <mripard@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/media/platform/broadcom/bcm2835-unicam.c | 41 ++++++++++++++++++------
 1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/drivers/media/platform/broadcom/bcm2835-unicam.c b/drivers/media/platform/broadcom/bcm2835-unicam.c
index 53a342853be6eeb99d62a777e2db41de8ce5da92..6710617f6e52c0f3716fd70c5b8af06c2dce31da 100644
--- a/drivers/media/platform/broadcom/bcm2835-unicam.c
+++ b/drivers/media/platform/broadcom/bcm2835-unicam.c
@@ -340,16 +340,16 @@ static const struct unicam_format_info unicam_image_formats[] = {
 		.code		= MEDIA_BUS_FMT_RGB565_1X16,
 		.depth		= 16,
 		.csi_dt		= MIPI_CSI2_DT_RGB565,
 	}, {
 		.fourcc		= V4L2_PIX_FMT_RGB24, /* rgb */
-		.code		= MEDIA_BUS_FMT_RGB888_1X24,
+		.code		= MEDIA_BUS_FMT_BGR888_1X24,
 		.depth		= 24,
 		.csi_dt		= MIPI_CSI2_DT_RGB888,
 	}, {
 		.fourcc		= V4L2_PIX_FMT_BGR24, /* bgr */
-		.code		= MEDIA_BUS_FMT_BGR888_1X24,
+		.code		= MEDIA_BUS_FMT_RGB888_1X24,
 		.depth		= 24,
 		.csi_dt		= MIPI_CSI2_DT_RGB888,
 	}, {
 	/* Bayer Formats */
 		.fourcc		= V4L2_PIX_FMT_SBGGR8,
@@ -2146,26 +2146,49 @@ static int unicam_video_link_validate(struct media_link *link)
 
 	if (is_image_node(node)) {
 		const struct v4l2_pix_format *fmt = &node->fmt.fmt.pix;
 		const struct unicam_format_info *fmtinfo;
 
-		fmtinfo = unicam_find_format_by_fourcc(fmt->pixelformat,
-						       UNICAM_SD_PAD_SOURCE_IMAGE);
+		fmtinfo = unicam_find_format_by_code(format->code,
+						     UNICAM_SD_PAD_SOURCE_IMAGE);
 		if (WARN_ON(!fmtinfo)) {
 			ret = -EPIPE;
 			goto out;
 		}
 
-		if (fmtinfo->code != format->code ||
-		    fmt->height != format->height ||
+		/*
+		 * Unicam initially associated BGR24 to BGR888_1X24 and RGB24 to
+		 * RGB888_1X24.
+		 *
+		 * In order to allow the applications using the old behaviour to
+		 * run, let's accept the old combination, but warn about it.
+		 */
+		if (fmtinfo->fourcc != fmt->pixelformat) {
+			if ((fmt->pixelformat == V4L2_PIX_FMT_BGR24 &&
+			     format->code == MEDIA_BUS_FMT_BGR888_1X24) ||
+			    (fmt->pixelformat == V4L2_PIX_FMT_RGB24 &&
+			     format->code == MEDIA_BUS_FMT_RGB888_1X24)) {
+				dev_warn_once(node->dev->dev,
+					      "Incorrect pixel format %p4cc for 0x%04x. Fix your application to use %p4cc.\n",
+					      &fmt->pixelformat, format->code, &fmtinfo->fourcc);
+			} else {
+				dev_dbg(node->dev->dev,
+					"image: format mismatch: 0x%04x <=> %p4cc\n",
+					format->code, &fmt->pixelformat);
+				ret = -EPIPE;
+				goto out;
+			}
+		}
+
+		if (fmt->height != format->height ||
 		    fmt->width != format->width ||
 		    fmt->field != format->field) {
 			dev_dbg(node->dev->dev,
-				"image: (%u x %u) 0x%08x %s != (%u x %u) 0x%08x %s\n",
-				fmt->width, fmt->height, fmtinfo->code,
+				"image: (%u x %u) %s != (%u x %u) %s\n",
+				fmt->width, fmt->height,
 				v4l2_field_names[fmt->field],
-				format->width, format->height, format->code,
+				format->width, format->height,
 				v4l2_field_names[format->field]);
 			ret = -EPIPE;
 		}
 	} else {
 		const struct v4l2_meta_format *fmt = &node->fmt.fmt.meta;

-- 
2.53.0