media: Zero-initialize all structures passed to subdev pad operations

Several drivers call subdev pad operations, passing structures that are
not fully zeroed. While the drivers initialize the fields they care
about explicitly, this results in reserved fields having uninitialized
values. Future kernel API changes that make use of those fields thus
risk breaking proper driver operation in ways that could be hard to
detect.

To avoid this, make the code more robust by zero-initializing all the
structures passed to subdev pad operation. Maintain a consistent coding
style by preferring designated initializers (which zero-initialize all
the fields that are not specified) over memset() where possible, and
make variable declarations local to inner scopes where applicable. One
notable exception to this rule is in the ipu3 driver, where a memset()
is needed as the structure is not a local variable but a function
parameter provided by the caller.

Not all fields of those structures can be initialized when declaring the
variables, as the values for those fields are computed later in the
code. Initialize the 'which' field in all cases, and other fields when
the variable declaration is so close to the v4l2_subdev_call() call that
it keeps all the context easily visible when reading the code, to avoid
hindering readability.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org> # For vimc
Reviewed-by: Lad Prabhakar <prabhakar.csengg@gmail.com> # For am437x
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de> # For drivers/staging/media/imx/
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

1 files changed, 16 insertions, 12 deletions

diff --git a/drivers/staging/media/imx/imx-media-capture.c b/drivers/staging/media/imx/imx-media-capture.c
index 93ba09236010..39666db59c4e 100644
--- a/drivers/staging/media/imx/imx-media-capture.c
+++ b/drivers/staging/media/imx/imx-media-capture.c
@@ -353,12 +353,13 @@ static int capture_legacy_enum_fmt_vid_cap(struct file *file, void *fh,
 {
 	struct capture_priv *priv = video_drvdata(file);
 	const struct imx_media_pixfmt *cc_src;
-	struct v4l2_subdev_format fmt_src;
+	struct v4l2_subdev_format fmt_src = {
+		.pad = priv->src_sd_pad,
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	u32 fourcc;
 	int ret;
 
-	fmt_src.pad = priv->src_sd_pad;
-	fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 	ret = v4l2_subdev_call(priv->src_sd, pad, get_fmt, NULL, &fmt_src);
 	if (ret) {
 		dev_err(priv->dev, "failed to get src_sd format\n");
@@ -426,11 +427,12 @@ static int capture_legacy_try_fmt_vid_cap(struct file *file, void *fh,
 					  struct v4l2_format *f)
 {
 	struct capture_priv *priv = video_drvdata(file);
-	struct v4l2_subdev_format fmt_src;
+	struct v4l2_subdev_format fmt_src = {
+		.pad = priv->src_sd_pad,
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	int ret;
 
-	fmt_src.pad = priv->src_sd_pad;
-	fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 	ret = v4l2_subdev_call(priv->src_sd, pad, get_fmt, NULL, &fmt_src);
 	if (ret)
 		return ret;
@@ -445,7 +447,10 @@ static int capture_legacy_s_fmt_vid_cap(struct file *file, void *fh,
 					struct v4l2_format *f)
 {
 	struct capture_priv *priv = video_drvdata(file);
-	struct v4l2_subdev_format fmt_src;
+	struct v4l2_subdev_format fmt_src = {
+		.pad = priv->src_sd_pad,
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	const struct imx_media_pixfmt *cc;
 	int ret;
 
@@ -454,8 +459,6 @@ static int capture_legacy_s_fmt_vid_cap(struct file *file, void *fh,
 		return -EBUSY;
 	}
 
-	fmt_src.pad = priv->src_sd_pad;
-	fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 	ret = v4l2_subdev_call(priv->src_sd, pad, get_fmt, NULL, &fmt_src);
 	if (ret)
 		return ret;
@@ -670,13 +673,14 @@ static void capture_buf_queue(struct vb2_buffer *vb)
 
 static int capture_validate_fmt(struct capture_priv *priv)
 {
-	struct v4l2_subdev_format fmt_src;
+	struct v4l2_subdev_format fmt_src = {
+		.pad = priv->src_sd_pad,
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	const struct imx_media_pixfmt *cc;
 	int ret;
 
 	/* Retrieve the media bus format on the source subdev. */
-	fmt_src.pad = priv->src_sd_pad;
-	fmt_src.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 	ret = v4l2_subdev_call(priv->src_sd, pad, get_fmt, NULL, &fmt_src);
 	if (ret)
 		return ret;