On Wed, Aug 17, 2011 at 10:41:51AM +0200, Guennadi Liakhovetski wrote: > On Sat, 6 Aug 2011, Sakari Ailus wrote: > > > Guennadi Liakhovetski wrote: > > > A possibility to preallocate and initialise buffers of different sizes > > > in V4L2 is required for an efficient implementation of asnapshot mode. > > > This patch adds two new ioctl()s: VIDIOC_CREATE_BUFS and > > > VIDIOC_PREPARE_BUF and defines respective data structures. > > > > > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx> > > > --- > > > > Hi Guennadi, > > [snip] > > > > + <para>When the I/O method is not supported the ioctl > > > +returns an &EINVAL;.</para> > > > + > > > + <table pgwide="1" frame="none" id="v4l2-create-buffers"> > > > + <title>struct <structname>v4l2_create_buffers</structname></title> > > > + <tgroup cols="3"> > > > + &cs-str; > > > + <tbody valign="top"> > > > + <row> > > > + <entry>__u32</entry> > > > + <entry><structfield>index</structfield></entry> > > > + <entry>The starting buffer index, returned by the driver.</entry> > > > + </row> > > > + <row> > > > + <entry>__u32</entry> > > > + <entry><structfield>count</structfield></entry> > > > + <entry>The number of buffers requested or granted.</entry> > > > + </row> > > > + <row> > > > + <entry>__u32</entry> > > > + <entry><structfield>type</structfield></entry> > > > + <entry>V4L2 buffer type: one of <constant>V4L2_BUF_TYPE_*</constant> > > > +values.</entry> > > > > &v4l2-buf-type; > > > > here? > > No idea and I don't care all that much, tbh. I certainly copy-pasted those > constructs from other documents, and yes, they are inconsistent across > v4l: some use my version, some yours, others <xref linkend=...>. I'm happy > with either or none of those. Just tell me _something_, that's > approapriate. Links are being used in other parts of V4L2 documentation. I think PREPARE_BUF documentation should use them, too, rather than duplicating parts of definitions. > > > > > + </row> > > > + <row> > > > + <entry>__u32</entry> > > > + <entry><structfield>memory</structfield></entry> > > > + <entry>Applications set this field to > > > +<constant>V4L2_MEMORY_MMAP</constant> or > > > +<constant>V4L2_MEMORY_USERPTR</constant>.</entry> > > > > &v4l2-memory; > > [snip] > > > > + <para>Applications can optionally call the > > > +<constant>VIDIOC_PREPARE_BUF</constant> ioctl to pass ownership of the buffer > > > +to the driver before actually enqueuing it, using the > > > +<constant>VIDIOC_QBUF</constant> ioctl, and to prepare it for future I/O. > > > > s/<constant>VIDIOC_QBUF</constant>/&VIDIOC_QBUF;/ > > *shrug* > > > > > +Such preparations may include cache invalidation or cleaning. Performing them > > > +in advance saves time during the actual I/O. In case such cache operations are > > > +not required, the application can use one of > > > +<constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant> and > > > +<constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant> flags to skip the respective > > > +step.</para> > > > + > > > + <para>The <structname>v4l2_buffer</structname> structure is > > > > s/<structname>v4l2_buffer</structname>/&v4l2-buffer;/ > > "structname" seems to be more precise, but well... It's precise but precision isn't everything: giving the user a link to the definition of e.g. v4l2_buffer is more useful than forcing him or her to look for it elsewhere in the documentation. These are small issues but the usability of the documentation counts a lot. Regards, -- Sakari Ailus sakari.ailus@xxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
