netdev - Re: [RFC 0/2] net: phy: Prevent an MDIO bus from being unloaded while in use

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Message-ID: <20140721185552.GA20027@arch.cereza>
Date:	Mon, 21 Jul 2014 15:55:53 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>
Subject: Re: [RFC 0/2] net: phy: Prevent an MDIO bus from being unloaded
 while in use

Hi Florian,

Thanks for the quick reply.

On 21 Jul 11:42 AM, Florian Fainelli wrote:
[..]
> >
> > This patchset fixes this by calling module_{get,put} in the ethernet driver.
> > After this patch, the mvmdio driver is no longer removable:
> >
> >   $ modprobe -r mvmdio
> >   modprobe: can't unload module mvmdio: Resource temporarily unavailable
> >
> > Of course, we can expect a few drivers to have the same need and therefore
> > we could argue about moving this to be part of the phydev connection.
> 
> Right, that's exactly what jumps to mind when I take a look at your
> patch set. As long as a PHY device connected to a particular MDIO bus
> is in used, we should make sure its refcount does not hit zero.
> 

Any suggestions about where to do it? I think the right place is
after the calls to bus_find_device() in of_phy_find_device() and
phy_connect().

> BTW, neither mvmdio nor mvneta seems to set their 'owner' field, is
> that intentional?
> 

Actually, I had a patch that did so and then dropped it. The owner
is set to unconditionally for plaftorm drivers, so setting it has no
effect. See include/linux/platform_device.h:

/*
 * use a macro to avoid include chaining to get THIS_MODULE
 */
#define platform_driver_register(drv) \
        __platform_driver_register(drv, THIS_MODULE)

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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