Re: [Linaro-mm-sig] [RFC/PATCH] fb: Add dma-buf support

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

[off-list ref] wrote:

quoted

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 <laurent.pinchart@ideasonboard.com>
---
 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