samples: usb: uvc: add filtering of the format

The UVC class now lets the application select the format list sent to the
host. Leverage this in the sample to filter out any format that is not
expected to work (buffer too big, rarely supported formats).

Signed-off-by: Josuah Demangeon <me@josuah.net>

Author: josuah

samples/subsys/usb/uvc/src/main.c

@@ -23,7 +23,28 @@ const static struct device *const video_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_cam
 /* Format capabilities of video_dev, used everywhere through the sample */
 static struct video_caps video_caps = {.type = VIDEO_BUF_TYPE_OUTPUT};
 
-static int app_add_format(uint32_t pixfmt, uint32_t width, uint32_t height)
+/* Pixel formats present in one of the UVC 1.5 standard */
+static bool app_is_supported_format(uint32_t pixfmt)
+{
+	return pixfmt == VIDEO_PIX_FMT_JPEG ||
+	       pixfmt == VIDEO_PIX_FMT_YUYV ||
+	       pixfmt == VIDEO_PIX_FMT_NV12;
+}
+
+static bool app_has_supported_format(void)
+{
+	const struct video_format_cap *fmts = video_caps.format_caps;
+
+	for (int i = 0; fmts[i].pixelformat != 0; i++) {
+		if (app_is_supported_format(fmts[i].pixelformat)) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static int app_add_format(uint32_t pixfmt, uint32_t width, uint32_t height, bool has_sup_fmts)
 {
 	struct video_format fmt = {
 		.pixelformat = pixfmt,
@@ -33,6 +54,11 @@ static int app_add_format(uint32_t pixfmt, uint32_t width, uint32_t height)
 	};
 	int ret;
 
+	/* If the system has any standard pixel format, only propose them to the host */
+	if (has_sup_fmts && !app_is_supported_format(pixfmt)) {
+		return;
+	}
+
 	/* Set the format to get the size */
 	ret = video_set_format(video_dev, &fmt);
 	if (ret != 0) {
@@ -58,16 +84,20 @@ static int app_add_format(uint32_t pixfmt, uint32_t width, uint32_t height)
 /* Submit to UVC only the formats expected to be working (enough memory for the size, etc.) */
 static int app_add_filtered_formats(void)
 {
+	const bool has_sup_fmts = app_has_supported_format();
+
 	for (int i = 0; video_caps.format_caps[i].pixelformat != 0; i++) {
 		const struct video_format_cap *vcap = &video_caps.format_caps[i];
 
-		ret = app_add_format(vcap->pixelformat, vcap->width_min, vcap->height_min);
+		ret = app_add_format(vcap->pixelformat, vcap->width_min, vcap->height_min,
+				     has_sup_fmts);
 		if (ret != 0) {
 			return ret;
 		}
 
 		if (vcap->width_min != vcap->width_max || vcap->height_min != vcap->height_max) {
-			ret = app_add_format(vcap->pixelformat, vcap->width_max, vcap->height_max);
+			ret = app_add_format(vcap->pixelformat, vcap->width_max, vcap->height_max,
+					     has_sup_fmts);
 			if (ret != 0) {
 				return ret;
 			}