Re: [PATCH v4 13/36] [media] v4l2: add a frame timeout event

From: Steve Longerbeam
Date: Thu Mar 09 2017 - 21:38:43 EST

On 03/05/2017 02:41 PM, Russell King - ARM Linux wrote:
On Sat, Mar 04, 2017 at 04:37:43PM -0800, Steve Longerbeam wrote:

On 03/04/2017 02:56 AM, Sakari Ailus wrote:
That's a bit of a special situation --- still there are alike conditions on
existing hardware. You should return the buffers to the user with the ERROR
flag set --- or return -EIO from VIDIOC_DQBUF, if the condition will

On i.MX an EOF timeout is not recoverable without a stream restart, so
I decided to call vb2_queue_error() when the timeout occurs (instead
of sending an event). The user will then get -EIO when it attempts to
queue or dequeue further buffers.

I'm not sure that statement is entirely accurate. With the IMX219
camera, I _could_ (with previous iterations of the iMX capture code)
stop it streaming, wait a while, and restart it, and everything
continues to work.

Hi Russell, did you see the "EOF timeout" kernel error message when you
stopped the IMX219 from streaming? Only a "EOF timeout" message
indicates the unrecoverable case.

Are you sure that the problem you have here is caused by the iMX6
rather than the ADV718x CVBS decoder (your initial description said
it was the decoder.)

Actually yes I did say it was the adv718x, but in fact I doubt the
adv718x has abruptly stopped data transmission on the bt.656 bus.
I actually suspect the IPU, specifically the CSI. In our experience
the CSI is rather sensitive to glitches and/or truncated frames on the
bt.656 bus and can easily loose vertical sync, and/or lock-up.


If it _is_ the decoder that's going wrong, that doesn't justify
cripping the rest of the driver for one instance of broken hardware
that _might_ be attached to it.