[PATCH 4/6] staging: bcm2835-v4l2: Add a TODO file for improvements we need.

Eric Anholt eric at anholt.net
Fri Jan 27 13:55:01 PST 2017

Signed-off-by: Eric Anholt <eric at anholt.net>
 drivers/staging/media/platform/bcm2835/TODO | 39 +++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 drivers/staging/media/platform/bcm2835/TODO

diff --git a/drivers/staging/media/platform/bcm2835/TODO b/drivers/staging/media/platform/bcm2835/TODO
new file mode 100644
index 000000000000..61a509992b9a
--- /dev/null
+++ b/drivers/staging/media/platform/bcm2835/TODO
@@ -0,0 +1,39 @@
+1) Support dma-buf memory management.
+In order to zero-copy import camera images into the 3D or display
+pipelines, we need to export our buffers through dma-buf so that the
+vc4 driver can import them.  This may involve bringing in the VCSM
+driver (which allows long-term management of regions of memory in the
+space that the VPU reserved and Linux otherwise doesn't have access
+to), or building some new protocol that allows VCSM-style management
+of Linux's CMA memory.
+2) Avoid extra copies for padding of images.
+We expose V4L2_PIX_FMT_* formats that have a specified stride/height
+padding in the V4L2 spec, but that padding doesn't match what the
+hardware can do.  If we exposed the native padding requirements
+through the V4L2 "multiplanar" formats, the firmware would have one
+less copy it needed to do.
+3) Port to ARM64
+The bulk_receive() does some manual cache flushing that are 32-bit ARM
+only, which we should convert to proper cross-platform APIs.
+4) Convert to be a platform driver.
+Right now when the module probes, it tries to initialize VCHI and
+errors out if it wasn't ready yet.  If bcm2835-v4l2 was built in, then
+VCHI generally isn't ready because it depends on both the firmware and
+mailbox drivers having already loaded.
+We should have VCHI create a platform device once it's initialized,
+and have this driver bind to it, so that we automatically load the
+v4l2 module after VCHI loads.
+5) Drop the gstreamer workaround.
+This was a temporary workaround for a bug that was fixed mid-2014, and
+we should remove it before stabilizing the driver.

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