samples: usb: uvc: add filtering of the format

The UVC class now allows the application to select the formats itself.
Leverage this from the sample to filter out any format that is not
expected to work (buffer too big) or less likely supported by the host
when more standard formats are available.

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

Author: josuah

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

@@ -32,7 +32,28 @@ static size_t app_get_min_buf_size(const struct video_format *const fmt)
 	}
 }
 
-static void app_add_format(uint32_t pixfmt, uint16_t width, uint16_t height)
+static bool app_is_standard_format(uint32_t pixfmt)
+{
+	return pixfmt == VIDEO_PIX_FMT_GREY || pixfmt == VIDEO_PIX_FMT_JPEG ||
+	       pixfmt == VIDEO_PIX_FMT_YUYV;
+}
+
+/* Check whether the video device supports one of the wisespread image sensor formats */
+static bool app_has_standard_formats(void)
+{
+	for (int i = 0;; i++) {
+		uint32_t pixfmt = video_caps.format_caps[i].pixelformat;
+
+		if (pixfmt == 0) {
+			return false;
+		}
+		if (app_is_standard_format(pixfmt)) {
+			return true;
+		}
+	}
+}
+
+static void app_add_format(uint32_t pixfmt, uint16_t width, uint16_t height, bool has_std_fmts)
 {
 	struct video_format fmt = {
 		.pixelformat = pixfmt,
@@ -42,6 +63,11 @@ static void app_add_format(uint32_t pixfmt, uint16_t width, uint16_t height)
 	};
 	int ret;
 
+	/* If the system has any standard pixel format, only propose them to the host */
+	if (has_std_fmts && !app_is_standard_format(pixfmt)) {
+		return;
+	}
+
 	/* Set the format to get the pitch */
 	ret = video_set_format(video_dev, &fmt);
 	if (ret != 0) {
@@ -60,13 +86,16 @@ static void app_add_format(uint32_t pixfmt, uint16_t width, uint16_t height)
 /* Submit to UVC only the formats expected to be working (enough memory for the size, etc.) */
 static void app_add_filtered_formats(void)
 {
+	const bool has_std_fmts = app_has_standard_formats();
+
 	for (int i = 0; video_caps.format_caps[i].pixelformat != 0; i++) {
 		const struct video_format_cap *vcap = &video_caps.format_caps[i];
 
-		app_add_format(vcap->pixelformat, vcap->width_min, vcap->height_min);
+		app_add_format(vcap->pixelformat, vcap->width_min, vcap->height_min, has_std_fmts);
 
 		if (vcap->width_min != vcap->width_max || vcap->height_min != vcap->height_max) {
-			app_add_format(vcap->pixelformat, vcap->width_max, vcap->height_max);
+			app_add_format(vcap->pixelformat, vcap->width_max, vcap->height_max,
+				       has_std_fmts);
 		}
 	}
 }