From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Date: Thu, 21 Jun 2012 08:46:15 +0000 Subject: Re: [Linaro-mm-sig] [RFC/PATCH] fb: Add dma-buf support Message-Id: <2493661.GRYQti1C6z@avalon> List-Id: References: <1340201368-20751-1-git-send-email-laurent.pinchart@ideasonboard.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jesse Barker Cc: linux-fbdev@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org Hi Jesse, Thank you for the review. On Wednesday 20 June 2012 08:09:19 Jesse Barker wrote: > Laurent, > > Your recent documentation efforts are extremely commendable. Just a > couple of small nits below... > > On Wed, Jun 20, 2012 at 7:09 AM, Laurent Pinchart > > wrote: > > Add support for the dma-buf exporter role to the frame buffer API. The > > importer role isn't meaningful for frame buffer devices, as the frame > > buffer device model doesn't allow using externally allocated memory. > > > > Signed-off-by: Laurent Pinchart > > --- > > Documentation/fb/api.txt | 36 ++++++++++++++++++++++++++++++++++++ > > drivers/video/fbmem.c | 36 ++++++++++++++++++++++++++++++++++++ > > include/linux/fb.h | 12 ++++++++++++ > > 3 files changed, 84 insertions(+), 0 deletions(-) > > > > diff --git a/Documentation/fb/api.txt b/Documentation/fb/api.txt > > index d4ff7de..f0b2173 100644 > > --- a/Documentation/fb/api.txt > > +++ b/Documentation/fb/api.txt > > @@ -304,3 +304,39 @@ extensions. > > Upon successful format configuration, drivers update the > > fb_fix_screeninfo > > type, visual and line_length fields depending on the selected format. The > > type and visual fields are set to FB_TYPE_FOURCC and FB_VISUAL_FOURCC > > respectively. + > > + > > +5. DMA buffer sharing > > +--------------------- > > + > > +The dma-buf kernel framework allows DMA buffers to be shared across > > devices +and applications. Sharing buffers across display devices and > > video capture or +video decoding devices allow zero-copy operation when > > displaying video content +produced by a hardware device such as a camera > > or a hardware codec. This is +crucial to achieve optimal system > > performances during video display. + > > +While dma-buf supports both exporting internally allocated memory as a > > dma-buf +object (known as the exporter role) and importing a dma-buf > > object to be used +as device memory (known as the importer role), the > > frame buffer API only +supports the exporter role, as the frame buffer > > device model doesn't support +using externally-allocated memory. > > + > > +The export a frame buffer as a dma-buf file descriptors, applications > > call the > s/The/To > s/descriptors/descriptor Fixed, thanks. -- Regards, Laurent Pinchart