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When reaching the end of stream, V4L2 clients may expect the V4L2_EOS_EVENT before being able to dequeue the last buffer, which has the V4L2_BUF_FLAG_LAST flag set. If the vb2_poll() function first checks for events and afterwards if buffers are available, a driver can queue the V4L2_EOS_EVENT event and return the buffer after the check for events but before the check for buffers. This causes vb2_poll() to signal that the buffer with V4L2_BUF_FLAG_LAST can be read without the V4L2_EOS_EVENT being available. First, check for available buffers and afterwards for events to ensure that if vb2_poll() signals POLLIN | POLLRDNORM for the V4L2_BUF_FLAG_LAST buffer, it also signals POLLPRI for the V4L2_EOS_EVENT. Signed-off-by: Michael Tretter <m.tretter@pengutronix.de> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.