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, 13 deletions

diff --git a/drivers/media/platform/ti/cal/cal-video.c b/drivers/media/platform/ti/cal/cal-video.c
index 4eade409d5d3..51ed82172d71 100644
--- a/drivers/media/platform/ti/cal/cal-video.c
+++ b/drivers/media/platform/ti/cal/cal-video.c
@@ -117,13 +117,13 @@ static int cal_legacy_enum_fmt_vid_cap(struct file *file, void *priv,
 static int __subdev_get_format(struct cal_ctx *ctx,
 			       struct v4l2_mbus_framefmt *fmt)
 {
-	struct v4l2_subdev_format sd_fmt;
+	struct v4l2_subdev_format sd_fmt = {
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+		.pad = 0,
+	};
 	struct v4l2_mbus_framefmt *mbus_fmt = &sd_fmt.format;
 	int ret;
 
-	sd_fmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
-	sd_fmt.pad = 0;
-
 	ret = v4l2_subdev_call(ctx->phy->source, pad, get_fmt, NULL, &sd_fmt);
 	if (ret)
 		return ret;
@@ -139,12 +139,13 @@ static int __subdev_get_format(struct cal_ctx *ctx,
 static int __subdev_set_format(struct cal_ctx *ctx,
 			       struct v4l2_mbus_framefmt *fmt)
 {
-	struct v4l2_subdev_format sd_fmt;
+	struct v4l2_subdev_format sd_fmt = {
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+		.pad = 0,
+	};
 	struct v4l2_mbus_framefmt *mbus_fmt = &sd_fmt.format;
 	int ret;
 
-	sd_fmt.which = V4L2_SUBDEV_FORMAT_ACTIVE;
-	sd_fmt.pad = 0;
 	*mbus_fmt = *fmt;
 
 	ret = v4l2_subdev_call(ctx->phy->source, pad, set_fmt, NULL, &sd_fmt);
@@ -190,7 +191,9 @@ static int cal_legacy_try_fmt_vid_cap(struct file *file, void *priv,
 {
 	struct cal_ctx *ctx = video_drvdata(file);
 	const struct cal_format_info *fmtinfo;
-	struct v4l2_subdev_frame_size_enum fse;
+	struct v4l2_subdev_frame_size_enum fse = {
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	int found;
 
 	fmtinfo = find_format_by_pix(ctx, f->fmt.pix.pixelformat);
@@ -209,7 +212,6 @@ static int cal_legacy_try_fmt_vid_cap(struct file *file, void *priv,
 	found = false;
 	fse.pad = 0;
 	fse.code = fmtinfo->code;
-	fse.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 	for (fse.index = 0; ; fse.index++) {
 		int ret;
 
@@ -302,7 +304,11 @@ static int cal_legacy_enum_framesizes(struct file *file, void *fh,
 {
 	struct cal_ctx *ctx = video_drvdata(file);
 	const struct cal_format_info *fmtinfo;
-	struct v4l2_subdev_frame_size_enum fse;
+	struct v4l2_subdev_frame_size_enum fse = {
+		.index = fsize->index,
+		.pad = 0,
+		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
+	};
 	int ret;
 
 	/* check for valid format */
@@ -313,10 +319,7 @@ static int cal_legacy_enum_framesizes(struct file *file, void *fh,
 		return -EINVAL;
 	}
 
-	fse.index = fsize->index;
-	fse.pad = 0;
 	fse.code = fmtinfo->code;
-	fse.which = V4L2_SUBDEV_FORMAT_ACTIVE;
 
 	ret = v4l2_subdev_call(ctx->phy->source, pad, enum_frame_size, NULL,
 			       &fse);