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[media] control.rst: improve the queryctrl code examples

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The code examples on how to enumerate controls were really long in the
tooth. Update them.

Using FLAG_NEXT_CTRL is preferred these days, so give that example first.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Hans Verkuil 2016-11-09 06:31:10 -02:00 committed by Mauro Carvalho Chehab
parent e92ca73b70
commit 93d39efdb1
1 changed files with 55 additions and 33 deletions
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88
Documentation/media/uapi/v4l/control.rst
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@ -312,21 +312,20 @@ more menu type controls.
.. _enum_all_controls:
Example: Enumerating all user controls
======================================
Example: Enumerating all controls
=================================
.. code-block:: c
struct v4l2_queryctrl queryctrl;
struct v4l2_querymenu querymenu;
static void enumerate_menu(void)
static void enumerate_menu(__u32 id)
{
printf(" Menu items:\\n");
memset(&querymenu, 0, sizeof(querymenu));
querymenu.id = queryctrl.id;
querymenu.id = id;
for (querymenu.index = queryctrl.minimum;
querymenu.index <= queryctrl.maximum;
@ -337,6 +336,55 @@ Example: Enumerating all user controls
}
}
memset(&queryctrl, 0, sizeof(queryctrl));
queryctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
while (0 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) {
if (!(queryctrl.flags & V4L2_CTRL_FLAG_DISABLED)) {
printf("Control %s\\n", queryctrl.name);
if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
enumerate_menu(queryctrl.id);
}
queryctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
}
if (errno != EINVAL) {
perror("VIDIOC_QUERYCTRL");
exit(EXIT_FAILURE);
}
Example: Enumerating all controls including compound controls
=============================================================
.. code-block:: c
struct v4l2_query_ext_ctrl query_ext_ctrl;
memset(&query_ext_ctrl, 0, sizeof(query_ext_ctrl));
query_ext_ctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL | V4L2_CTRL_FLAG_NEXT_COMPOUND;
while (0 == ioctl(fd, VIDIOC_QUERY_EXT_CTRL, &query_ext_ctrl)) {
if (!(query_ext_ctrl.flags & V4L2_CTRL_FLAG_DISABLED)) {
printf("Control %s\\n", query_ext_ctrl.name);
if (query_ext_ctrl.type == V4L2_CTRL_TYPE_MENU)
enumerate_menu(query_ext_ctrl.id);
}
query_ext_ctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL | V4L2_CTRL_FLAG_NEXT_COMPOUND;
}
if (errno != EINVAL) {
perror("VIDIOC_QUERY_EXT_CTRL");
exit(EXIT_FAILURE);
}
Example: Enumerating all user controls (old style)
==================================================
.. code-block:: c
memset(&queryctrl, 0, sizeof(queryctrl));
for (queryctrl.id = V4L2_CID_BASE;
@ -349,7 +397,7 @@ Example: Enumerating all user controls
printf("Control %s\\n", queryctrl.name);
if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
enumerate_menu();
enumerate_menu(queryctrl.id);
} else {
if (errno == EINVAL)
continue;
@ -368,7 +416,7 @@ Example: Enumerating all user controls
printf("Control %s\\n", queryctrl.name);
if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
enumerate_menu();
enumerate_menu(queryctrl.id);
} else {
if (errno == EINVAL)
break;
@ -379,32 +427,6 @@ Example: Enumerating all user controls
}
Example: Enumerating all user controls (alternative)
====================================================
.. code-block:: c
memset(&queryctrl, 0, sizeof(queryctrl));
queryctrl.id = V4L2_CTRL_CLASS_USER | V4L2_CTRL_FLAG_NEXT_CTRL;
while (0 == ioctl(fd, VIDIOC_QUERYCTRL, &queryctrl)) {
if (V4L2_CTRL_ID2CLASS(queryctrl.id) != V4L2_CTRL_CLASS_USER)
break;
if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED)
continue;
printf("Control %s\\n", queryctrl.name);
if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
enumerate_menu();
queryctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
}
if (errno != EINVAL) {
perror("VIDIOC_QUERYCTRL");
exit(EXIT_FAILURE);
}
Example: Changing controls
==========================