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

Message-ID: <20181213101832.00352dc2@xeon-e3>
Date:   Thu, 13 Dec 2018 10:18:32 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Jan Petrous <jan.petrous@....com>
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?

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.