path: root/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
diff options
authorSakari Ailus <sakari.ailus@iki.fi>2012-05-10 02:02:07 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2012-05-14 08:09:02 -0300
commit6016af82eafcb6e086a8f2a2197b46029a843d68 (patch)
treea8133e0651a8e0d5d33fbce904471a9c42127b51 /Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
parent121b3ddbe4ad17df77cb7284239be0a63d9a66bd (diff)
[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>
Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml')
1 files changed, 3 insertions, 2 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml b/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
index 18b1a8266f7..407dfceb71f 100644
--- a/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
@@ -73,10 +73,11 @@ same value as in the &v4l2-input; <structfield>tuner</structfield>
field and the &v4l2-tuner; <structfield>index</structfield> field.</entry>
- <entry>&v4l2-tuner-type;</entry>
+ <entry>__u32</entry>
<entry>The tuner type. This is the same value as in the
-&v4l2-tuner; <structfield>type</structfield> field.</entry>
+&v4l2-tuner; <structfield>type</structfield> field. See <xref
+ linkend="v4l2-tuner-type" /></entry>