mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2025-01-25 10:09:41 +07:00
6016af82ea
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>
166 lines
5.4 KiB
XML
166 lines
5.4 KiB
XML
<refentry id="vidioc-cropcap">
|
|
<refmeta>
|
|
<refentrytitle>ioctl VIDIOC_CROPCAP</refentrytitle>
|
|
&manvol;
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>VIDIOC_CROPCAP</refname>
|
|
<refpurpose>Information about the video cropping and scaling abilities</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>int <function>ioctl</function></funcdef>
|
|
<paramdef>int <parameter>fd</parameter></paramdef>
|
|
<paramdef>int <parameter>request</parameter></paramdef>
|
|
<paramdef>struct v4l2_cropcap
|
|
*<parameter>argp</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Arguments</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>fd</parameter></term>
|
|
<listitem>
|
|
<para>&fd;</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>request</parameter></term>
|
|
<listitem>
|
|
<para>VIDIOC_CROPCAP</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>argp</parameter></term>
|
|
<listitem>
|
|
<para></para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>Applications use this function to query the cropping
|
|
limits, the pixel aspect of images and to calculate scale factors.
|
|
They set the <structfield>type</structfield> field of a v4l2_cropcap
|
|
structure to the respective buffer (stream) type and call the
|
|
<constant>VIDIOC_CROPCAP</constant> ioctl with a pointer to this
|
|
structure. Drivers fill the rest of the structure. The results are
|
|
constant except when switching the video standard. Remember this
|
|
switch can occur implicit when switching the video input or
|
|
output.</para>
|
|
|
|
<table pgwide="1" frame="none" id="v4l2-cropcap">
|
|
<title>struct <structname>v4l2_cropcap</structname></title>
|
|
<tgroup cols="3">
|
|
&cs-str;
|
|
<tbody valign="top">
|
|
<row>
|
|
<entry>__u32</entry>
|
|
<entry><structfield>type</structfield></entry>
|
|
<entry>Type of the data stream, set by the application.
|
|
Only these types are valid here:
|
|
<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
|
|
<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
|
|
<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver
|
|
defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
|
|
and higher. See <xref linkend="v4l2-buf-type" />.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry>
|
|
<entry><structfield>bounds</structfield></entry>
|
|
<entry>Defines the window within capturing or output is
|
|
possible, this may exclude for example the horizontal and vertical
|
|
blanking areas. The cropping rectangle cannot exceed these limits.
|
|
Width and height are defined in pixels, the driver writer is free to
|
|
choose origin and units of the coordinate system in the analog
|
|
domain.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry>
|
|
<entry><structfield>defrect</structfield></entry>
|
|
<entry>Default cropping rectangle, it shall cover the
|
|
"whole picture". Assuming pixel aspect 1/1 this could be for example a
|
|
640 × 480 rectangle for NTSC, a
|
|
768 × 576 rectangle for PAL and SECAM centered over
|
|
the active picture area. The same co-ordinate system as for
|
|
<structfield>bounds</structfield> is used.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>&v4l2-fract;</entry>
|
|
<entry><structfield>pixelaspect</structfield></entry>
|
|
<entry><para>This is the pixel aspect (y / x) when no
|
|
scaling is applied, the ratio of the actual sampling
|
|
frequency and the frequency required to get square
|
|
pixels.</para><para>When cropping coordinates refer to square pixels,
|
|
the driver sets <structfield>pixelaspect</structfield> to 1/1. Other
|
|
common values are 54/59 for PAL and SECAM, 11/10 for NTSC sampled
|
|
according to [<xref linkend="itu601" />].</para></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<!-- NB this table is duplicated in the overlay chapter. -->
|
|
|
|
<table pgwide="1" frame="none" id="v4l2-rect-crop">
|
|
<title>struct <structname>v4l2_rect</structname></title>
|
|
<tgroup cols="3">
|
|
&cs-str;
|
|
<tbody valign="top">
|
|
<row>
|
|
<entry>__s32</entry>
|
|
<entry><structfield>left</structfield></entry>
|
|
<entry>Horizontal offset of the top, left corner of the
|
|
rectangle, in pixels.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>__s32</entry>
|
|
<entry><structfield>top</structfield></entry>
|
|
<entry>Vertical offset of the top, left corner of the
|
|
rectangle, in pixels.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>__s32</entry>
|
|
<entry><structfield>width</structfield></entry>
|
|
<entry>Width of the rectangle, in pixels.</entry>
|
|
</row>
|
|
<row>
|
|
<entry>__s32</entry>
|
|
<entry><structfield>height</structfield></entry>
|
|
<entry>Height of the rectangle, in pixels. Width
|
|
and height cannot be negative, the fields are signed for
|
|
hysterical reasons. <!-- video4linux-list@redhat.com
|
|
on 22 Oct 2002 subject "Re:[V4L][patches!] Re:v4l2/kernel-2.5" -->
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
&return-value;
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><errorcode>EINVAL</errorcode></term>
|
|
<listitem>
|
|
<para>The &v4l2-cropcap; <structfield>type</structfield> is
|
|
invalid. This is not permitted for video capture, output and overlay devices,
|
|
which must support <constant>VIDIOC_CROPCAP</constant>.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
</refentry>
|