Re: [PATCH 2/2] dma: add Qualcomm Technologies HIDMA channel driver

[Arnd Bergmann <arnd@arndb.de>]

On Friday 30 October 2015 17:36:45 Timur Tabi wrote:
> On 10/30/2015 05:28 PM, Arnd Bergmann wrote:
> >>> > >Why ENODEV? Could you make this handle restarted system calls?
> >> >
> >> >This is the self test code. It gets called from probe. If there is a
> >> >problem with the device or system configuration, I don't want to enable
> >> >this device. I can certainly return a different error code though.
> >> >What's a good code?
> > I see. probe() is not restartable, so it cannot be -ERESTARTSYS.
> >
> > Maybe better use wait_event_timeout and not handle the signals then.
> > It will eventually time out if something goes wrong.
> 
> What about -EPROBE_DEFER?  Isn't that "restartable"?  Granted, it's only 
> supposed to be used if the driver is dependent on another driver to 
> probe, so I'm not sure it applies here.  If the self-test fails, then it 
> is possible that it could succeed later?

No, this is different. The probe function can get called from all sorts
of contexts (sys_init_module, device_create, deferred probing), and not
all of them go back to user space when returning an error, so we cannot
deliver a signal to the calling process this way.

	Arnd