Re: Question regarding linux1394 and bug report

[Adam G. <ad...@po...>]

Hi Tasos,

On Sun, Jan 21, 2024 at 08:05:48PM +0200, Tasos Sahanidis wrote:
> The following is from 2.6.35-rc3 on Ubuntu 10.10:
...
> [  530.690859] firewire_ohci: IRQ 00000080 IR

OK, that's the video transmission that was missing from the previous 
message.

> This is a typical failed capture attempt on newer kernels (6.7):
> $ dvgrab -noavc -guid 00808801035809f1 -d 1
> libiec61883 warning: Transmission node has no plugs online!
...
> [ 3313.955351] firewire_ohci 0000:01:03.0: AT spd 0 tl 35, ffc1 -> ffc0, ack_pending , QR req, fffff0000904
> [ 3313.956255] firewire_ohci 0000:01:03.0: IRQ 00000020 AR_resp
> [ 3313.956261] firewire_ohci 0000:01:03.0: AR spd 0 tl 35, ffc0 -> ffc1, ack_complete, QR resp = 003f007a

The camera's oPCR0 register (the response to the read of '904) has the 
online and broadcast bits clear, indicating that the output plug will 
not be sending any video. I wonder why? (Compare to the value c03f3c7a 
in the 2.6.35-rc3 case, which has the online and broadcast bits set.)

What do the 6.7 logs look like when the camera is first turned on, 
starting with the first evt_bus_reset?

> At the moment I suspect there might be a race somewhere.

I agree, it must be timing related. That explains why it was affected by 
the seemingly unrelated workqueue change.

-- Adam