netdev - Re: [PATCH v2 net-next 01/14] qed: convert link mode from u32 to bitmap

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Date:   Mon, 20 Jul 2020 18:29:30 +0300
From:   Alexander Lobakin <alobakin@...vell.com>
To:     Joe Perches <joe@...ches.com>
CC:     Alexander Lobakin <alobakin@...vell.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Igor Russkikh <irusskikh@...vell.com>,
        Michal Kalderon <michal.kalderon@...vell.com>,
        Ariel Elior <aelior@...vell.com>,
        "Denis Bolotin" <denis.bolotin@...vell.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        <GR-everest-linux-l2@...vell.com>,
        <QLogic-Storage-Upstream@...vell.com>, <netdev@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 net-next 01/14] qed: convert link mode from u32 to bitmap

Hi Joe,

From: Joe Perches <joe@...ches.com>
Date: Mon, 20 Jul 2020 08:19:52 -0700

> On Mon, 2020-07-20 at 12:23 +0300, Alexander Lobakin wrote:
>> Date: Sun, 19 Jul 2020 23:21:00 +0200 From: Andrew Lunn <andrew@...n.ch>
>>> On Sun, Jul 19, 2020 at 11:14:40PM +0300, Alexander Lobakin wrote:
>>>> Currently qed driver already ran out of 32 bits to store link modes,
>>>> and this doesn't allow to add and support more speeds.
>>>> Convert link mode to bitmap that will always have enough space for
>>>> any number of speeds and modes.
> []
>>> Why not just throw away all these QED_LM_ defines and use the kernel
>>> link modes? The fact you are changing the u32 to a bitmap suggests the
>>> hardware does not use them.
>> 
>> I've just double-checked, and you're right, management firmware operates
>> with NVM_* definitions, while QED_LM_* are used only in QED and QEDE to
>> fill Ethtool link settings.
>> I didn't notice this while working on the series, but it would be really
>> a lot better to just use generic definitions.
>> So I'll send v3 soon.
>
> While you're at it, why are you using __set_bit and not set_bit?

Because I'm filling link modes and don't need any atomicity at all.
If you refer linkmode_*() functions [1], they also use non-atomic
variants of bitops.

Al

[1] https://elixir.bootlin.com/linux/v5.8-rc4/source/include/linux/linkmode.h