netdev - Re: napi driver for multiport device with the only one dma channel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <c1030f43df31cce16ce96b460cd6fccb633e69e5.camel@nxp.com>
Date:   Fri, 14 Dec 2018 08:09:48 +0000
From:   Jan Petrous <jan.petrous@....com>
To:     "stephen@...workplumber.org" <stephen@...workplumber.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: napi driver for  multiport device with the only one dma channel -
 is it possible?

Hi Steven.

On Thu, 2018-12-13 at 10:18 -0800, Stephen Hemminger wrote:
> On Thu, 13 Dec 2018 13:30:50 +0000
> Jan Petrous <jan.petrous@....com> wrote:
> 
> > Hi,
> > 
> > am I understand it right that I can not use NAPI-powered design in
> > case
> > when there is only one rx queue and one tx queue (only two
> > dma channels) usable for data transfer with the ethernet controller
> > for
> > all interfaces (2 ports or more)?
> > 
> > I could imagine there would be possibility to declare for example
> > rx
> > queue sharable between napi interfaces, but I was not able to find
> > anything like that.
> > 
> > I agree that it is a bit strange configuration but we have to
> > support
> > such corner case (when other dma channels are used by independent
> > systems).
> > 
> > I seems like I have to create two drivers - one with napi, when at
> > least the same number of dma channels are free for use and second
> > one
> > without napi (because of not enough dma channels).
> > 
> > 
> > Thanks.
> > /Jan
> 
> It is possible. Sky2 for some hardware has a single NAPI (on port 0)
> and if the card is dual port the napi of port 0 is used by port 1.

Thanks for the hint. It is exactly what I was searching for.

/Jan