[media] v4l: Support extending the v4l2_pix_format structure

The v4l2_pix_format structure has no reserved field. It is embedded in
the v4l2_framebuffer structure which has no reserved fields either, and
in the v4l2_format structure which has reserved fields that were not
previously required to be zeroed out by applications.

To allow extending v4l2_pix_format, inline it in the v4l2_framebuffer
structure, and use the priv field as a magic value to indicate that the
application has set all v4l2_pix_format extended fields and zeroed all
reserved fields following the v4l2_pix_format field in the v4l2_format
structure.

The availability of this API extension is reported to userspace through
the new V4L2_CAP_EXT_PIX_FORMAT capability flag. Just checking that the
priv field is still set to the magic value at [GS]_FMT return wouldn't
be enough, as older kernels don't zero the priv field on return.

To simplify the internal API towards drivers zero the extended fields
and set the priv field to the magic value for applications not aware of
the extensions.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

1 files changed, 61 insertions, 4 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 96bc117f66b2..2e630005676f 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -973,13 +973,48 @@ static int check_fmt(struct file *file, enum v4l2_buf_type type)
 	return -EINVAL;
 }
 
+static void v4l_sanitize_format(struct v4l2_format *fmt)
+{
+	unsigned int offset;
+
+	/*
+	 * The v4l2_pix_format structure has been extended with fields that were
+	 * not previously required to be set to zero by applications. The priv
+	 * field, when set to a magic value, indicates the the extended fields
+	 * are valid. Otherwise they will contain undefined values. To simplify
+	 * the API towards drivers zero the extended fields and set the priv
+	 * field to the magic value when the extended pixel format structure
+	 * isn't used by applications.
+	 */
+
+	if (fmt->type != V4L2_BUF_TYPE_VIDEO_CAPTURE &&
+	    fmt->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
+		return;
+
+	if (fmt->fmt.pix.priv == V4L2_PIX_FMT_PRIV_MAGIC)
+		return;
+
+	fmt->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+
+	offset = offsetof(struct v4l2_pix_format, priv)
+	       + sizeof(fmt->fmt.pix.priv);
+	memset(((void *)&fmt->fmt.pix) + offset, 0,
+	       sizeof(fmt->fmt.pix) - offset);
+}
+
 static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
 				struct file *file, void *fh, void *arg)
 {
 	struct v4l2_capability *cap = (struct v4l2_capability *)arg;
+	int ret;
 
 	cap->version = LINUX_VERSION_CODE;
-	return ops->vidioc_querycap(file, fh, cap);
+
+	ret = ops->vidioc_querycap(file, fh, cap);
+
+	cap->capabilities |= V4L2_CAP_EXT_PIX_FORMAT;
+
+	return ret;
 }
 
 static int v4l_s_input(const struct v4l2_ioctl_ops *ops,
@@ -1103,12 +1138,17 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_sdr = vfd->vfl_type == VFL_TYPE_SDR;
 	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
+	int ret;
+
+	p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
 
 	switch (p->type) {
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_g_fmt_vid_cap))
 			break;
-		return ops->vidioc_g_fmt_vid_cap(file, fh, arg);
+		ret = ops->vidioc_g_fmt_vid_cap(file, fh, arg);
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_g_fmt_vid_cap_mplane))
 			break;
@@ -1128,7 +1168,9 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_g_fmt_vid_out))
 			break;
-		return ops->vidioc_g_fmt_vid_out(file, fh, arg);
+		ret = ops->vidioc_g_fmt_vid_out(file, fh, arg);
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_g_fmt_vid_out_mplane))
 			break;
@@ -1163,6 +1205,8 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
 
+	v4l_sanitize_format(p);
+
 	switch (p->type) {
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_s_fmt_vid_cap))
@@ -1233,6 +1277,8 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
 
+	v4l_sanitize_format(p);
+
 	switch (p->type) {
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_try_fmt_vid_cap))
@@ -1516,7 +1562,18 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
 	struct v4l2_create_buffers *create = arg;
 	int ret = check_fmt(file, create->format.type);
 
-	return ret ? ret : ops->vidioc_create_bufs(file, fh, create);
+	if (ret)
+		return ret;
+
+	v4l_sanitize_format(&create->format);
+
+	ret = ops->vidioc_create_bufs(file, fh, create);
+
+	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
+	    create->format.type == V4L2_BUF_TYPE_VIDEO_OUTPUT)
+		create->format.fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+
+	return ret;
 }
 
 static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,