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    SubjectRe: [PATCH/RFC] core: add a function to safely try to get device driver owner
    On Mon, Nov 29, 2010 at 09:54:10PM +0100, Guennadi Liakhovetski wrote:
    > Hi Jon
    > On Mon, 29 Nov 2010, Jonathan Corbet wrote:
    > > On Mon, 29 Nov 2010 20:43:28 +0100 (CET)
    > > Guennadi Liakhovetski <> wrote:
    > >
    > > > When two drivers interoperate without an explicit dependency, it is often
    > > > required to prevent one of them from being unloaded safely by dereferencing
    > > > dev->driver->owner. This patch provides a generic function to do this in a
    > > > race-free way.
    > >
    > > I must ask: why not, instead, make the dependency explicit? In
    > > particular, this looks like an application for the proposed media
    > > controller code, which is meant to model the connections between otherwise
    > > independent devices. The fact that your example comes from V4L2 (which is
    > > the current domain of the media controller) also argues that way.
    > Sorry, don't see a good way to do this. This function is for a general
    > dependency, where you don't have that driver, we are checking for register
    > with us, so, the only way to get to it is via dev->driver->owner.

    Wait, what? The device is already bound to a driver, right, so why
    would you care about "locking" the module into memory? What could this
    possibly be used for?

    > And I also don't want to move registering the device into the
    > dependant driver and then wait (with a timeout) for a driver to probe
    > with it... I just want to verify, whether a driver has attached to
    > that device and whether I can lock it down.

    Who cares if a driver is attached to any device? And again, why would
    you want to "lock it down"?


    greg k-h

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