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

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Date:   Thu, 13 Dec 2018 13:30:50 +0000
From:   Jan Petrous <jan.petrous@....com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: napi driver for  multiport device with the only one dma channel - is
 it possible?

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