From 6016af82eafcb6e086a8f2a2197b46029a843d68 Mon Sep 17 00:00:00 2001 From: Sakari Ailus Date: Thu, 10 May 2012 02:02:07 -0300 Subject: [media] v4l2: use __u32 rather than enums in ioctl() structs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: 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: 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 Signed-off-by: Sakari Ailus Acked-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/DocBook/media/v4l/vidioc-cropcap.xml | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'Documentation/DocBook/media/v4l/vidioc-cropcap.xml') diff --git a/Documentation/DocBook/media/v4l/vidioc-cropcap.xml b/Documentation/DocBook/media/v4l/vidioc-cropcap.xml index b4f2f255211..f1bac2c6e97 100644 --- a/Documentation/DocBook/media/v4l/vidioc-cropcap.xml +++ b/Documentation/DocBook/media/v4l/vidioc-cropcap.xml @@ -65,7 +65,7 @@ output. &cs-str; - &v4l2-buf-type; + __u32 type Type of the data stream, set by the application. Only these types are valid here: @@ -73,7 +73,7 @@ Only these types are valid here: V4L2_BUF_TYPE_VIDEO_OUTPUT, V4L2_BUF_TYPE_VIDEO_OVERLAY, and custom (driver defined) types with code V4L2_BUF_TYPE_PRIVATE -and higher. +and higher. See . struct v4l2_rect -- cgit v1.2.3