[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>
diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
index 2829d25..89ae433 100644
--- a/drivers/media/video/v4l2-compat-ioctl32.c
+++ b/drivers/media/video/v4l2-compat-ioctl32.c
@@ -37,7 +37,7 @@
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 @@
}
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_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_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;