On Wed, 28 Sep 2011, Sakari Ailus wrote: > Hi Guennadi, > > What's your opinion on this? I was intended to complement the PREPARE_BUF > documentation. I don't think I have a very strong opinion about this. AFAIU this is so far just a (yet another) speculation about what the driver might want or need to do in PREPARE_BUF. Let's wait until the author of these patches manages to get them straight (...) and until all the reviewers are satisfied:-) Then you're certainly welcome to submit any improvement you see fit, then the usual suspects will express their opinions on them. So, business as usual, I would say;-) Thanks Guennadi > > On Thu, Sep 01, 2011 at 02:08:56PM +0300, Sakari Ailus wrote: > > Add note to documentation of VIDIOC_PREPARE_BUF that the preparation done by > > the IOCTL may include locking buffers to system memory and creating DMA > > mappings for them. > > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxx> > > --- > > .../DocBook/media/v4l/vidioc-prepare-buf.xml | 8 +++++--- > > 1 files changed, 5 insertions(+), 3 deletions(-) > > > > diff --git a/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml > > index 509e752..7177c2f 100644 > > --- a/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml > > +++ b/Documentation/DocBook/media/v4l/vidioc-prepare-buf.xml > > @@ -52,9 +52,11 @@ > > <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. > > -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 > > +Such preparations may include locking the buffer to system memory and > > +creating DMA mapping for it (on the first time > > +<constant>VIDIOC_PREPARE_BUF</constant> is called), 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> > > -- > > 1.7.2.5 > > > > -- > > 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 > > -- > Sakari Ailus > e-mail: sakari.ailus@xxxxxx jabber/XMPP/Gmail: sailus@xxxxxxxxxxxxxx > --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- 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
