netdev - Re: [PATCH 4/4] asix: Add a new driver for the AX88172A

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: <CABkLObo5v00QKo-X7hEVbMcXA_QwKFA6HfL-Le5VvU2J5Cs2eg@mail.gmail.com>
Date:	Wed, 11 Jul 2012 10:27:44 +0200
From:	Christian Riesch <christian.riesch@...cron.at>
To:	michael@...sch.at
Cc:	Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org,
	Oliver Neukum <oneukum@...e.de>,
	Eric Dumazet <edumazet@...gle.com>,
	Allan Chou <allan@...x.com.tw>,
	Mark Lord <kernel@...savvy.com>,
	Grant Grundler <grundler@...omium.org>,
	Ming Lei <tom.leiming@...il.com>
Subject: Re: [PATCH 4/4] asix: Add a new driver for the AX88172A

Hi Ben and Michael,

On Mon, Jul 9, 2012 at 12:30 PM, Christian Riesch
<christian.riesch@...cron.at> wrote:
> Hi Ben and Michael,
>
> On Sun, Jul 8, 2012 at 5:39 PM, Michael Riesch <michael@...sch.at> wrote:
>> On Fri, 2012-07-06 at 18:37 +0100, Ben Hutchings wrote:
>>> > +   priv->mdio->priv = (void *)dev;
>>> > +   priv->mdio->read = &asix_mdio_bus_read;
>>> > +   priv->mdio->write = &asix_mdio_bus_write;
>>> > +   priv->mdio->name = "Asix MDIO Bus";
>>> > +   snprintf(priv->mdio->id, MII_BUS_ID_SIZE, "asix-%s",
>>> > +            dev_name(dev->net->dev.parent));
>>> [...]
>>>
>>> I think you need to ensure that the bus identifier is unique throughout
>>> its lifetime, but net devices can be renamed and that could lead to a
>>> collision.  Perhaps you could use the ifindex or the USB device path
>>
>> Ben,
>>
>> the dev_name function in the code above returns the sysfs filename of
>> the USB device (e.g. 1-0:1.0).
>>
>>> (though that might be too long).
>>
>> This may be a problem. The bus identifier may be 17 characters long, so
>> if we leave the endpoint/configuration part (:1.0) and the prefix away
>> it should be fine in any "normal" system. However, on a system with a
>> more-than-9-root-hubs 5-tier 127-devices-each USB infrastructure it
>> results in collisions. So is this approach acceptable?
>>
>> Using the ifindex sounds good to me,
>>
>> snprintf(priv->mdio->id, MII_BUS_ID_SIZE, "asix-%d",
>>         dev->net->ifindex);
>>
>> works on any system with less than 10^12 network interfaces.
>
> Ok, I'll change that to use ifindex.

No, I won't.
At the time the mdio bus is registered, ifindex is not yet set, so the
snprintf would always result in "asix-0".

Any ideas?
Should I keep the dev_name(dev->net->dev.parent) and hope that nobody
uses that many USB devices/hubs so that it is short enough? Or use
some other solution? A global counter in ax88172a.c that numbers the
mdio busses (asix-0, asix-1...)?

Regards, Christian
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html