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[media] V4L: Improve the selection API documentation
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Make the VIDIOC_G/S_SELECTION ioctls documentation more consistent
with the rest of media Docbook, use capital letters where necessary
and correct few minor errors.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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Sylwester Nawrocki authored and Mauro Carvalho Chehab committed Mar 19, 2012
1 parent 1d53160 commit 9080d5d
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8 changes: 6 additions & 2 deletions Documentation/DocBook/media/v4l/selection-api.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,10 @@ cropping and composing rectangles have the same size.</para>
</textobject>
</mediaobject>
</figure>

For complete list of the available selection targets see table <xref
linkend="v4l2-sel-target"/>

</section>

<section>
Expand Down Expand Up @@ -186,7 +190,7 @@ V4L2_SEL_TGT_COMPOSE_ACTIVE </constant> target.</para>

<section>

<title>Scaling control.</title>
<title>Scaling control</title>

<para>An application can detect if scaling is performed by comparing the width
and the height of rectangles obtained using <constant> V4L2_SEL_TGT_CROP_ACTIVE
Expand All @@ -200,7 +204,7 @@ the scaling ratios using these values.</para>

<section>

<title>Comparison with old cropping API.</title>
<title>Comparison with old cropping API</title>

<para>The selection API was introduced to cope with deficiencies of previous
<link linkend="crop"> API </link>, that was designed to control simple capture
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106 changes: 55 additions & 51 deletions Documentation/DocBook/media/v4l/vidioc-g-selection.xml
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Expand Up @@ -58,43 +58,43 @@

<para>The ioctls are used to query and configure selection rectangles.</para>

<para> To query the cropping (composing) rectangle set <structfield>
&v4l2-selection;::type </structfield> to the respective buffer type. Do not
use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE
<para> To query the cropping (composing) rectangle set &v4l2-selection;
<structfield> type </structfield> field to the respective buffer type.
Do not use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE
</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of
<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is
setting <structfield> &v4l2-selection;::target </structfield> to value
<constant> V4L2_SEL_TGT_CROP_ACTIVE </constant> (<constant>
setting the value of &v4l2-selection; <structfield>target</structfield> field
to <constant> V4L2_SEL_TGT_CROP_ACTIVE </constant> (<constant>
V4L2_SEL_TGT_COMPOSE_ACTIVE </constant>). Please refer to table <xref
linkend="v4l2-sel-target" /> or <xref linkend="selection-api" /> for additional
targets. Fields <structfield> &v4l2-selection;::flags </structfield> and
<structfield> &v4l2-selection;::reserved </structfield> are ignored and they
must be filled with zeros. The driver fills the rest of the structure or
targets. The <structfield>flags</structfield> and <structfield>reserved
</structfield> fields of &v4l2-selection; are ignored and they must be filled
with zeros. The driver fills the rest of the structure or
returns &EINVAL; if incorrect buffer type or target was used. If cropping
(composing) is not supported then the active rectangle is not mutable and it is
always equal to the bounds rectangle. Finally, structure <structfield>
&v4l2-selection;::r </structfield> is filled with the current cropping
always equal to the bounds rectangle. Finally, the &v4l2-rect;
<structfield>r</structfield> rectangle is filled with the current cropping
(composing) coordinates. The coordinates are expressed in driver-dependent
units. The only exception are rectangles for images in raw formats, whose
coordinates are always expressed in pixels. </para>

<para> To change the cropping (composing) rectangle set <structfield>
&v4l2-selection;::type </structfield> to the respective buffer type. Do not
<para> To change the cropping (composing) rectangle set the &v4l2-selection;
<structfield>type</structfield> field to the respective buffer type. Do not
use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE
</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of
<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is
setting <structfield> &v4l2-selection;::target </structfield> to value
<constant> V4L2_SEL_TGT_CROP_ACTIVE </constant> (<constant>
setting the value of &v4l2-selection; <structfield>target</structfield> to
<constant>V4L2_SEL_TGT_CROP_ACTIVE</constant> (<constant>
V4L2_SEL_TGT_COMPOSE_ACTIVE </constant>). Please refer to table <xref
linkend="v4l2-sel-target" /> or <xref linkend="selection-api" /> for additional
targets. Set desired active area into the field <structfield>
&v4l2-selection;::r </structfield>. Field <structfield>
&v4l2-selection;::reserved </structfield> is ignored and must be filled with
zeros. The driver may adjust the rectangle coordinates. An application may
introduce constraints to control rounding behaviour. Set the field
<structfield> &v4l2-selection;::flags </structfield> to one of values:
targets. The &v4l2-rect; <structfield>r</structfield> rectangle need to be
set to the desired active area. Field &v4l2-selection; <structfield> reserved
</structfield> is ignored and must be filled with zeros. The driver may adjust
coordinates of the requested rectangle. An application may
introduce constraints to control rounding behaviour. The &v4l2-selection;
<structfield>flags</structfield> field must be set to one of the following:

<itemizedlist>
<listitem>
Expand Down Expand Up @@ -129,7 +129,7 @@ and vertical offset and sizes are chosen according to following priority:

<orderedlist>
<listitem>
<para>Satisfy constraints from <structfield>&v4l2-selection;::flags</structfield>.</para>
<para>Satisfy constraints from &v4l2-selection; <structfield>flags</structfield>.</para>
</listitem>
<listitem>
<para>Adjust width, height, left, and top to hardware limits and alignments.</para>
Expand All @@ -145,7 +145,7 @@ and vertical offset and sizes are chosen according to following priority:
</listitem>
</orderedlist>

On success the field <structfield> &v4l2-selection;::r </structfield> contains
On success the &v4l2-rect; <structfield>r</structfield> field contains
the adjusted rectangle. When the parameters are unsuitable the application may
modify the cropping (composing) or image parameters and repeat the cycle until
satisfactory parameters have been negotiated. If constraints flags have to be
Expand All @@ -162,38 +162,38 @@ exist no rectangle </emphasis> that satisfies the constraints.</para>
<tbody valign="top">
<row>
<entry><constant>V4L2_SEL_TGT_CROP_ACTIVE</constant></entry>
<entry>0</entry>
<entry>area that is currently cropped by hardware</entry>
<entry>0x0000</entry>
<entry>The area that is currently cropped by hardware.</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_CROP_DEFAULT</constant></entry>
<entry>1</entry>
<entry>suggested cropping rectangle that covers the "whole picture"</entry>
<entry>0x0001</entry>
<entry>Suggested cropping rectangle that covers the "whole picture".</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_CROP_BOUNDS</constant></entry>
<entry>2</entry>
<entry>limits for the cropping rectangle</entry>
<entry>0x0002</entry>
<entry>Limits for the cropping rectangle.</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_COMPOSE_ACTIVE</constant></entry>
<entry>256</entry>
<entry>area to which data are composed by hardware</entry>
<entry>0x0100</entry>
<entry>The area to which data is composed by hardware.</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_COMPOSE_DEFAULT</constant></entry>
<entry>257</entry>
<entry>suggested composing rectangle that covers the "whole picture"</entry>
<entry>0x0101</entry>
<entry>Suggested composing rectangle that covers the "whole picture".</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_COMPOSE_BOUNDS</constant></entry>
<entry>258</entry>
<entry>limits for the composing rectangle</entry>
<entry>0x0102</entry>
<entry>Limits for the composing rectangle.</entry>
</row>
<row>
<entry><constant>V4L2_SEL_TGT_COMPOSE_PADDED</constant></entry>
<entry>259</entry>
<entry>the active area and all padding pixels that are inserted or modified by the hardware</entry>
<entry>0x0103</entry>
<entry>The active area and all padding pixels that are inserted or modified by hardware.</entry>
</row>
</tbody>
</tgroup>
Expand All @@ -209,12 +209,14 @@ exist no rectangle </emphasis> that satisfies the constraints.</para>
<row>
<entry><constant>V4L2_SEL_FLAG_GE</constant></entry>
<entry>0x00000001</entry>
<entry>indicate that adjusted rectangle must contain a rectangle from <structfield>&v4l2-selection;::r</structfield></entry>
<entry>Indicates that the adjusted rectangle must contain the original
&v4l2-selection; <structfield>r</structfield> rectangle.</entry>
</row>
<row>
<entry><constant>V4L2_SEL_FLAG_LE</constant></entry>
<entry>0x00000002</entry>
<entry>indicate that adjusted rectangle must be inside a rectangle from <structfield>&v4l2-selection;::r</structfield></entry>
<entry>Indicates that the adjusted rectangle must be inside the original
&v4l2-rect; <structfield>r</structfield> rectangle.</entry>
</row>
</tbody>
</tgroup>
Expand Down Expand Up @@ -245,27 +247,29 @@ exist no rectangle </emphasis> that satisfies the constraints.</para>
<row>
<entry>__u32</entry>
<entry><structfield>type</structfield></entry>
<entry>Type of the buffer (from &v4l2-buf-type;)</entry>
<entry>Type of the buffer (from &v4l2-buf-type;).</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>target</structfield></entry>
<entry>used to select between <link linkend="v4l2-sel-target"> cropping and composing rectangles </link></entry>
<entry>Used to select between <link linkend="v4l2-sel-target"> cropping
and composing rectangles</link>.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>flags</structfield></entry>
<entry>control over coordinates adjustments, refer to <link linkend="v4l2-sel-flags">selection flags</link></entry>
<entry>Flags controlling the selection rectangle adjustments, refer to
<link linkend="v4l2-sel-flags">selection flags</link>.</entry>
</row>
<row>
<entry>&v4l2-rect;</entry>
<entry><structfield>r</structfield></entry>
<entry>selection rectangle</entry>
<entry>The selection rectangle.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved[9]</structfield></entry>
<entry>Reserved fields for future use</entry>
<entry>Reserved fields for future use.</entry>
</row>
</tbody>
</tgroup>
Expand All @@ -278,24 +282,24 @@ exist no rectangle </emphasis> that satisfies the constraints.</para>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The buffer <structfield> &v4l2-selection;::type </structfield>
or <structfield> &v4l2-selection;::target </structfield> is not supported, or
the <structfield> &v4l2-selection;::flags </structfield> are invalid.</para>
<para>Given buffer type <structfield>type</structfield> or
the selection target <structfield>target</structfield> is not supported,
or the <structfield>flags</structfield> argument is not valid.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>ERANGE</errorcode></term>
<listitem>
<para>it is not possible to adjust a rectangle <structfield>
&v4l2-selection;::r </structfield> that satisfies all contraints from
<structfield> &v4l2-selection;::flags </structfield>.</para>
<para>It is not possible to adjust &v4l2-rect; <structfield>
r</structfield> rectangle to satisfy all contraints given in the
<structfield>flags</structfield> argument.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>EBUSY</errorcode></term>
<listitem>
<para>it is not possible to apply change of selection rectangle at the moment.
Usually because streaming is in progress.</para>
<para>It is not possible to apply change of the selection rectangle
at the moment. Usually because streaming is in progress.</para>
</listitem>
</varlistentry>
</variablelist>
Expand Down
30 changes: 15 additions & 15 deletions include/linux/videodev2.h
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Original file line number Diff line number Diff line change
Expand Up @@ -762,20 +762,20 @@ struct v4l2_crop {

/* Selection targets */

/* current cropping area */
#define V4L2_SEL_TGT_CROP_ACTIVE 0
/* default cropping area */
#define V4L2_SEL_TGT_CROP_DEFAULT 1
/* cropping bounds */
#define V4L2_SEL_TGT_CROP_BOUNDS 2
/* current composing area */
#define V4L2_SEL_TGT_COMPOSE_ACTIVE 256
/* default composing area */
#define V4L2_SEL_TGT_COMPOSE_DEFAULT 257
/* composing bounds */
#define V4L2_SEL_TGT_COMPOSE_BOUNDS 258
/* current composing area plus all padding pixels */
#define V4L2_SEL_TGT_COMPOSE_PADDED 259
/* Current cropping area */
#define V4L2_SEL_TGT_CROP_ACTIVE 0x0000
/* Default cropping area */
#define V4L2_SEL_TGT_CROP_DEFAULT 0x0001
/* Cropping bounds */
#define V4L2_SEL_TGT_CROP_BOUNDS 0x0002
/* Current composing area */
#define V4L2_SEL_TGT_COMPOSE_ACTIVE 0x0100
/* Default composing area */
#define V4L2_SEL_TGT_COMPOSE_DEFAULT 0x0101
/* Composing bounds */
#define V4L2_SEL_TGT_COMPOSE_BOUNDS 0x0102
/* Current composing area plus all padding pixels */
#define V4L2_SEL_TGT_COMPOSE_PADDED 0x0103

/**
* struct v4l2_selection - selection info
Expand All @@ -785,7 +785,7 @@ struct v4l2_crop {
* @r: coordinates of selection window
* @reserved: for future use, rounds structure size to 64 bytes, set to zero
*
* Hardware may use multiple helper window to process a video stream.
* Hardware may use multiple helper windows to process a video stream.
* The structure is used to exchange this selection areas between
* an application and a driver.
*/
Expand Down

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