[media] em28xx: implement VIDIOC_ENUM_FRAMESIZES

Pidgin uses gstreamer (and libv4l) to work. Without implementing this ioctl,
it won't detect properly the size range, and driver will fail.

So, this patch is required, in order to use an em27xx webcam, like
Silvercrest.

The pigdin/gstreamer/libv4l needs to be fixed, as it shouldn't assume
that all drivers will implement this optional ioctl, but, at least now,
devices with em28xx have a better chance of working with pidgin.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-video.c

@@ -1802,6 +1802,45 @@ static int vidioc_enum_fmt_vid_cap(struct file *file, void  *priv,
 	return 0;
 }
 
+static int vidioc_enum_framesizes(struct file *file, void *priv,
+				  struct v4l2_frmsizeenum *fsize)
+{
+	struct em28xx_fh      *fh  = priv;
+	struct em28xx         *dev = fh->dev;
+	struct em28xx_fmt     *fmt;
+	unsigned int	      maxw = norm_maxw(dev);
+	unsigned int	      maxh = norm_maxh(dev);
+
+	fmt = format_by_fourcc(fsize->pixel_format);
+	if (!fmt) {
+		em28xx_videodbg("Fourcc format (%08x) invalid.\n",
+				fsize->pixel_format);
+		return -EINVAL;
+	}
+
+	if (dev->board.is_em2800) {
+		if (fsize->index > 1)
+			return -EINVAL;
+		fsize->type = V4L2_FRMSIZE_TYPE_DISCRETE;
+		fsize->discrete.width = maxw / (1 + fsize->index);
+		fsize->discrete.height = maxh / (1 + fsize->index);
+		return 0;
+	}
+
+	if (fsize->index != 0)
+		return -EINVAL;
+
+	/* Report a continuous range */
+	fsize->type = V4L2_FRMSIZE_TYPE_STEPWISE;
+	fsize->stepwise.min_width = 48;
+	fsize->stepwise.min_height = 32;
+	fsize->stepwise.max_width = maxw;
+	fsize->stepwise.max_height = maxh;
+	fsize->stepwise.step_width = 1;
+	fsize->stepwise.step_height = 1;
+	return 0;
+}
+
 /* Sliced VBI ioctls */
 static int vidioc_g_fmt_sliced_vbi_cap(struct file *file, void *priv,
 					struct v4l2_format *f)
@@ -2356,10 +2395,10 @@ static const struct v4l2_ioctl_ops video_ioctl_ops = {
 	.vidioc_s_fmt_vid_cap       = vidioc_s_fmt_vid_cap,
 	.vidioc_g_fmt_vbi_cap       = vidioc_g_fmt_vbi_cap,
 	.vidioc_s_fmt_vbi_cap       = vidioc_s_fmt_vbi_cap,
+	.vidioc_enum_framesizes     = vidioc_enum_framesizes,
 	.vidioc_g_audio             = vidioc_g_audio,
 	.vidioc_s_audio             = vidioc_s_audio,
 	.vidioc_cropcap             = vidioc_cropcap,
-
 	.vidioc_g_fmt_sliced_vbi_cap   = vidioc_g_fmt_sliced_vbi_cap,
 	.vidioc_try_fmt_sliced_vbi_cap = vidioc_try_set_sliced_vbi_cap,
 	.vidioc_s_fmt_sliced_vbi_cap   = vidioc_try_set_sliced_vbi_cap,