netdev - Re: [Socketcan-users] poll broken (for can)

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Message-ID: <20110330074623.GB339@kurt.e-circ.dyndns.org>
Date:	Wed, 30 Mar 2011 09:46:23 +0200
From:	Kurt Van Dijck <kurt.van.dijck@....be>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	Marc Kleine-Budde <mkl@...gutronix.de>, Netdev@...r.kernel.org,
	socketcan-users@...ts.berlios.de,
	Wolfgang Grandegger <wg@...ndegger.com>
Subject: Re: [Socketcan-users] poll broken (for can)

On Tue, Mar 29, 2011 at 10:03:12PM +0200, Oliver Hartkopp wrote:
> On 28.03.2011 21:32, Marc Kleine-Budde wrote:
> > On 03/28/2011 07:53 PM, Oliver Hartkopp wrote:
> >> On 28.03.2011 18:13, Marc Kleine-Budde wrote:
> >>> On 03/28/2011 05:55 PM, Wolfgang Grandegger wrote:

> > What do we really want to specify?
> 
> Hm - the problem could be that people expect their frames to be sent 'in
> time', so if we increase the tx_queue_len, it's not transparent when the
> frames are potentially leaving the system - and if the application data is
> already out-dated when hitting the medium.
> 
> What about having up to three CAN frames in each CAN_RAW socket send buffer
> and e.g.50 frames in the tx_queue_len of the netdevice as a starting point?
50 looks good, but 3 is a bit small IMHO.
> 
> 
> > 
> > Something like: queue up to X frames per socket and queue only Y frames
> > per device. Where Y = X * n and n is "I don't know yet"?
> > 
> > Y is simple, it's the tx_queue_len. But X is more complicated. The can
> > frames have non constant length (i.e. dlc) and I'm not sure that the
> > netdev people say if we misuse the sock_alloc_send_pskb() for our
> > tx-flow-control :)
> 
> I would propose to count the CAN frames independently from the can_dlc.
ack.
> AFAIK
> the tx_queue_len is dealing with skb's - and the skb->len for the socket send
> buffer is also size of struct can_frame, right?
ack.
> 
> Regards,
> Oliver
> 
> _______________________________________________
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> Socketcan-users@...ts.berlios.de
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