media: vimc: Add support for contiguous DMA buffers

The vimc driver is used for testing purpose, and some test use cases
involve sharing buffers with a consumer device. Consumers often require
DMA contiguous memory, which vimc doesn't currently support. This leads
in the best case to usage of bounce buffers, which is very slow, and in
the worst case in a complete failure.

Add support for the dma-contig allocator in vimc to support those use
cases properly. The allocator is selected through a new "allocator"
module parameter, which defaults to vmalloc.

[hverkuil: add missing 'select VIDEOBUF2_DMA_CONFIG' to Kconfig]

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/vimc.rst b/Documentation/admin-guide/media/vimc.rst
index 180507d455f2..0b07f05dde25 100644
--- a/Documentation/admin-guide/media/vimc.rst
+++ b/Documentation/admin-guide/media/vimc.rst
@@ -76,3 +76,16 @@ vimc-capture:
 
 	* 1 Pad sink
 	* 1 Pad source
+
+Module options
+--------------
+
+Vimc has a module parameter to configure the driver.
+
+* ``allocator=<unsigned int>``
+
+	memory allocator selection, default is 0. It specifies the way buffers
+	will be allocated.
+
+		- 0: vmalloc
+		- 1: dma-contig