linux-kernel - Re: [PATCH] net: fec: defer probe if PHY on external MDIO bus is not available

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: <7a478c1f25d2ea96ff09cee77d648e9c63b97dcf.camel@ew.tq-group.com>
Date:   Fri, 22 Oct 2021 09:57:54 +0200
From:   Matthias Schiffer <matthias.schiffer@...tq-group.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Joakim Zhang <qiangqing.zhang@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: fec: defer probe if PHY on external MDIO bus is
 not available

On Thu, 2021-10-21 at 14:50 +0200, Andrew Lunn wrote:
> > I would love to do this, but driver-api/driver-model/driver.rst
> > contains the following warning:
> > 
> >       -EPROBE_DEFER must not be returned if probe() has already created
> >       child devices, even if those child devices are removed again
> >       in a cleanup path. If -EPROBE_DEFER is returned after a child
> >       device has been registered, it may result in an infinite loop of
> >       .probe() calls to the same driver.
> > 
> > My understanding of this is that there is simply no way to return
> > -EPROBE_DEFER after fec_enet_mii_init(pdev).
> 
> It might say that, but lots of network drivers actually do this. I've
> not seen an endless loop.
> 
>     Andrew


Hmm, lots of network drivers? I tried to find an example, but all
drivers that generate -EPROBE_DEFER for missing PHYs at all don't have
an internal MDIO bus and thus avoid the circular dependency.

Matthias