media: ti-vpe: vpe: fix a v4l2-compliance warning about invalid pixel format

v4l2-compliance warns with this message:

   warn: v4l2-test-formats.cpp(717): \
 	TRY_FMT cannot handle an invalid pixelformat.
   warn: v4l2-test-formats.cpp(718): \
 	This may or may not be a problem. For more information see:
   warn: v4l2-test-formats.cpp(719): \
 	http://www.mail-archive.com/linux-media@vger.kernel.org/msg56550.html
	...
   test VIDIOC_TRY_FMT: FAIL

We need to make sure that the returns a valid pixel format in all
instance. Based on the v4l2 framework convention drivers must return a
valid pixel format when the requested pixel format is either invalid or
not supported.
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/ti-vpe/vpe.c

@@ -351,20 +351,25 @@ enum {
 };
 
 /* find our format description corresponding to the passed v4l2_format */
-static struct vpe_fmt *find_format(struct v4l2_format *f)
+static struct vpe_fmt *__find_format(u32 fourcc)
 {
 	struct vpe_fmt *fmt;
 	unsigned int k;
 
 	for (k = 0; k < ARRAY_SIZE(vpe_formats); k++) {
 		fmt = &vpe_formats[k];
-		if (fmt->fourcc == f->fmt.pix.pixelformat)
+		if (fmt->fourcc == fourcc)
 			return fmt;
 	}
 
 	return NULL;
 }
 
+static struct vpe_fmt *find_format(struct v4l2_format *f)
+{
+	return __find_format(f->fmt.pix.pixelformat);
+}
+
 /*
  * there is one vpe_dev structure in the driver, it is shared by
  * all instances.
@@ -1599,9 +1604,9 @@ static int __vpe_try_fmt(struct vpe_ctx *ctx, struct v4l2_format *f,
 	unsigned int stride = 0;
 
 	if (!fmt || !(fmt->types & type)) {
-		vpe_err(ctx->dev, "Fourcc format (0x%08x) invalid.\n",
+		vpe_dbg(ctx->dev, "Fourcc format (0x%08x) invalid.\n",
 			pix->pixelformat);
-		return -EINVAL;
+		fmt = __find_format(V4L2_PIX_FMT_YUYV);
 	}
 
 	if (pix->field != V4L2_FIELD_NONE &&