Re: [PATCH] iio: Simplify IIO provider access locking mechanism

Ivan T. Ivanov
2015-01-09T16:14:45Z

On Fri, 2015-01-09 at 16:54 +0100, Lars-Peter Clausen wrote:
> On 01/09/2015 04:50 PM, Ivan T. Ivanov wrote:
> > On Fri, 2015-01-09 at 16:41 +0100, Lars-Peter Clausen wrote:
> > > On 01/09/2015 04:38 PM, Ivan T. Ivanov wrote:
> > > > Instead of checking whether provider module is still
> > > > loaded on every access to device just lock module to
> > > > memory when client get reference to provider device.
> > > >
> > >
> > > This has nothing to do with the module, it's about the device. In the Linux
> > > device driver model as device can be unbound at any time and the IIO
> > > framework needs to handle this.
> > >
> >
> > Hm. Probably i am missing something here, but is this
> > still true if we have reference to device structure?
>
> Yes, that only prevents the memory of device from being freed. But the
> device can still be unbound from the driver.
>
> Think of e.g. a USB device that is pulled from the USB connector. Nothing
> you can do in software about having the device disappear.
>

Agree, but I think that the patch is still valid. Module
have to be pinned in memory as long as there are device
driver users.

Regards,
Ivan