Re: Problem using raw1394_iso_recv_init() - the irq_interval parameter

[Alexander N. <neu...@kd...>]

On Tuesday 10 January 2012, Stefan Richter wrote:
> On Jan 10 Clemens Ladisch wrote:
> > Alexander Neundorf wrote:
> > > I seem to have a strange problem with the irq_interval parameter of
> > > raw1394_iso_recv_init().
> > > It seems to have an upper limit of 512. Is that possible ?
> > 
> > No, this parameter itself does not have an upper limit.
> > 
> > > If I set it to higher values than that, I still get the callback after
> > > 512 packets have arrived.
> > 
> > Actually, you get the callback after the correct number of packets.
> > What you do not get is information about more than 512 of those packets.
> > 
> > It would have been a good idea to document juju's 4 KB limit ...
> 
> Clemens refers to an implementation limit deep down in the firewire-ohci
> controller driver.  There is a per-context temporary buffer used to
> generate the "isochronous packets received" events.  This buffer holds
> isochronous packet header data and timestamps (usually 4 + 4 bytes per
> packet) and is one page size big (usually 4 kBytes).

Thanks for the quick reply, knowing that there is really this limit is 
basically good enough for me.
Should I write a patch for libraw1394 which documents this ?

Alex