[media] v4l2: use __u32 rather than enums in ioctl() structs

V4L2 uses the enum type in IOCTL arguments in IOCTLs that were defined until
the use of enum was considered less than ideal. Recently Rémi Denis-Courmont
brought up the issue by proposing a patch to convert the enums to unsigned:

<URL:http://www.spinics.net/lists/linux-media/msg46167.html>

This sparked a long discussion where another solution to the issue was
proposed: two sets of IOCTL structures, one with __u32 and the other with
enums, and conversion code between the two:

<URL:http://www.spinics.net/lists/linux-media/msg47168.html>

Both approaches implement a complete solution that resolves the problem. The
first one is simple but requires assuming enums and __u32 are the same in
size (so we won't break the ABI) while the second one is more complex and
less clean but does not require making that assumption.

The issue boils down to whether enums are fundamentally different from __u32
or not, and can the former be substituted by the latter. During the
discussion it was concluded that the __u32 has the same size as enums on all
archs Linux is supported: it has not been shown that replacing those enums
in IOCTL arguments would break neither source or binary compatibility. If no
such reason is found, just replacing the enums with __u32s is the way to go.

This is what this patch does. This patch is slightly different from Remi's
first RFC (link above): it uses __u32 instead of unsigned and also changes
the arguments of VIDIOC_G_PRIORITY and VIDIOC_S_PRIORITY.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
index 2829d256e4b7..89ae433877e6 100644
--- a/drivers/media/video/v4l2-compat-ioctl32.c
+++ b/drivers/media/video/v4l2-compat-ioctl32.c
@@ -37,7 +37,7 @@ struct v4l2_clip32 {
 
 struct v4l2_window32 {
 	struct v4l2_rect        w;
-	enum v4l2_field  	field;
+	__u32		  	field;	/* enum v4l2_field */
 	__u32			chromakey;
 	compat_caddr_t		clips; /* actually struct v4l2_clip32 * */
 	__u32			clipcount;
@@ -147,7 +147,7 @@ static inline int put_v4l2_sliced_vbi_format(struct v4l2_sliced_vbi_format *kp,
 }
 
 struct v4l2_format32 {
-	enum v4l2_buf_type type;
+	__u32	type;	/* enum v4l2_buf_type */
 	union {
 		struct v4l2_pix_format	pix;
 		struct v4l2_pix_format_mplane	pix_mp;
@@ -170,7 +170,7 @@ struct v4l2_format32 {
 struct v4l2_create_buffers32 {
 	__u32			index;
 	__u32			count;
-	enum v4l2_memory        memory;
+	__u32			memory;	/* enum v4l2_memory */
 	struct v4l2_format32	format;
 	__u32			reserved[8];
 };
@@ -311,16 +311,16 @@ struct v4l2_plane32 {
 
 struct v4l2_buffer32 {
 	__u32			index;
-	enum v4l2_buf_type      type;
+	__u32			type;	/* enum v4l2_buf_type */
 	__u32			bytesused;
 	__u32			flags;
-	enum v4l2_field		field;
+	__u32			field;	/* enum v4l2_field */
 	struct compat_timeval	timestamp;
 	struct v4l2_timecode	timecode;
 	__u32			sequence;
 
 	/* memory location */
-	enum v4l2_memory        memory;
+	__u32			memory;	/* enum v4l2_memory */
 	union {
 		__u32           offset;
 		compat_long_t   userptr;