mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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5bd4bb7817
LaTeX doesn't handle too well auto-width on tables, and ReST
markup requires an special tag to give it the needed hints.
As we're using A4 paper, we have 17cm of useful spaces. As
most media tables have widths, let's use it to generate the
needed via the following perl script:
my ($line_size, $table_header, $has_cols) = (17.5, 0, 0);
my $out;
my $header = "";
my @widths = ();
sub round { $_[0] > 0 ? int($_[0] + .5) : -int(-$_[0] + .5) }
while (<>) {
if (!$table_header) {
$has_cols = 1 if (m/..\s+tabularcolumns::/);
if (m/..\s+flat-table::/) {
$table_header = 1;
$header = $_;
next;
}
$out .= $_;
next;
}
$header .= $_;
@widths = split(/ /, $1) if (m/:widths:\s+(.*)/);
if (m/^\n$/) {
if (!$has_cols && @widths) {
my ($tot, $t, $i) = (0, 0, 0);
foreach my $v(@widths) { $tot += $v; };
$out .= ".. tabularcolumns:: |";
for ($i = 0; $i < scalar @widths - 1; $i++) {
my $v = $widths[$i];
my $w = round(10 * ($v * $line_size) / $tot) / 10;
$out .= sprintf "p{%.1fcm}|", $w;
$t += $w;
}
my $w = $line_size - $t;
$out .= sprintf "p{%.1fcm}|\n\n", $w;
}
$out .= $header;
$table_header = 0;
$has_cols = 0;
$header = "";
@widths = ();
}
}
print $out;
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
128 lines
3.5 KiB
ReStructuredText
128 lines
3.5 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_REQBUFS:
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********************
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ioctl VIDIOC_REQBUFS
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********************
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Name
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====
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VIDIOC_REQBUFS - Initiate Memory Mapping, User Pointer I/O or DMA buffer I/O
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Synopsis
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========
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.. cpp:function:: int ioctl( int fd, int request, struct v4l2_requestbuffers *argp )
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``request``
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VIDIOC_REQBUFS
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``argp``
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Description
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===========
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This ioctl is used to initiate :ref:`memory mapped <mmap>`,
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:ref:`user pointer <userp>` or :ref:`DMABUF <dmabuf>` based I/O.
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Memory mapped buffers are located in device memory and must be allocated
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with this ioctl before they can be mapped into the application's address
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space. User buffers are allocated by applications themselves, and this
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ioctl is merely used to switch the driver into user pointer I/O mode and
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to setup some internal structures. Similarly, DMABUF buffers are
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allocated by applications through a device driver, and this ioctl only
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configures the driver into DMABUF I/O mode without performing any direct
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allocation.
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To allocate device buffers applications initialize all fields of the
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:ref:`struct v4l2_requestbuffers <v4l2-requestbuffers>` structure. They set the ``type``
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field to the respective stream or buffer type, the ``count`` field to
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the desired number of buffers, ``memory`` must be set to the requested
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I/O method and the ``reserved`` array must be zeroed. When the ioctl is
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called with a pointer to this structure the driver will attempt to
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allocate the requested number of buffers and it stores the actual number
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allocated in the ``count`` field. It can be smaller than the number
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requested, even zero, when the driver runs out of free memory. A larger
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number is also possible when the driver requires more buffers to
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function correctly. For example video output requires at least two
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buffers, one displayed and one filled by the application.
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When the I/O method is not supported the ioctl returns an ``EINVAL`` error
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code.
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Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
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buffers, however this cannot succeed when any buffers are still mapped.
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A ``count`` value of zero frees all buffers, after aborting or finishing
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any DMA in progress, an implicit
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:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`.
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.. _v4l2-requestbuffers:
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. flat-table:: struct v4l2_requestbuffers
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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- .. row 1
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- __u32
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- ``count``
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- The number of buffers requested or granted.
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- .. row 2
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- __u32
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- ``type``
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- Type of the stream or buffers, this is the same as the struct
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:ref:`v4l2_format <v4l2-format>` ``type`` field. See
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:ref:`v4l2-buf-type` for valid values.
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- .. row 3
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- __u32
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- ``memory``
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- Applications set this field to ``V4L2_MEMORY_MMAP``,
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``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See
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:ref:`v4l2-memory`.
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- .. row 4
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- __u32
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- ``reserved``\ [2]
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- A place holder for future extensions. Drivers and applications
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must set the array to zero.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The buffer type (``type`` field) or the requested I/O method
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(``memory``) is not supported.
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