netdev - Re: [PATCH net-next v2 05/10] bnxt_en: Fix ethtool -l|-L inconsistent channel counts.

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Message-ID: <20160920155214.3ea1e280@jkicinski-Precision-T1700>
Date:   Tue, 20 Sep 2016 15:52:14 +0100
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Michael Chan <michael.chan@...adcom.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        "Mintz, Yuval" <Yuval.Mintz@...ium.com>
Subject: Re: [PATCH net-next v2 05/10] bnxt_en: Fix ethtool -l|-L
 inconsistent channel counts.

Hi!

On Tue, 20 Sep 2016 02:50:23 -0400, Michael Chan wrote:
> The existing code is inconsistent in reporting and accepting the combined
> channel count.  bnxt_get_channels() reports maximum combined as the
> maximum rx count.  bnxt_set_channels() accepts combined count that
> cannot be bigger than max rx or max tx.
> 
> For example, if max rx = 2 and max tx = 1, we report max supported
> combined to be 2.  But if the user tries to set combined to 2, it will
> fail because 2 is bigger than max tx which is 1.
> 
> Fix the code to be consistent.  Max allowed combined = max(max_rx, max_tx).
> We will accept a combined channel count <= max(max_rx, max_tx).
> 
> Signed-off-by: Michael Chan <michael.chan@...adcom.com>

Sorry I wasn't able to respond in time but I'm with Yuval on this one.

The canonical meaning for the parameters is set by man page for ethtool:
>        rx N   Changes the number of channels with only receive queues.
> 
>        tx N   Changes the number of channels with only transmit queues.
> 
>        other N
>               Changes the number of channels used only for other purposes e.g.
>               link interrupts or SR-IOV co-ordination.
> 
>        combined N
>               Changes the number of multi-purpose channels.

Could we please agree that combined means having both RX and TX and the
others mean having only the specified one?  See for example:

e261768e9e39 ("be2net: support asymmetric rx/tx queue counts")