On Wed, 9 Oct 2019, Bastien Nocera wrote:
> On Wed, 2019-10-09 at 13:28 -0400, Alan Stern wrote:
> <snip>
> > No, that's not quite it.
> >
> > Here's what should happen when the subclass driver is being probed:
> > First, call the generic_probe routine, and return immediately if that
> > fails. Then call the subclass driver's probe routine. If that gets
> > an
> > error, fail the probe call but tell the device core that the device
> > is
> > now bound to the generic driver, not to the subclass driver.
>
> So, something like that, on top of the existing patches? (I'm not sure
> whether device_driver_attach is the correct call to use here).
>
> - if (udriver->probe)
> - return udriver->probe(udev);
> - return 0;
> + if (!udriver->probe)
> + return 0;
This test is unnecessary; all drivers must have a probe routine.
Otherwise how would they know when they get bound to a device?
> + error = udriver->probe(udev);
> + if (error == -ENODEV &&
> + udrv != &usb_generic_driver)
No need to test for usb_generic_driver; its probe routine always
returns 0. But if you want to include the test anyway, at least don't
split the line -- it will all fit in under 80 columns.
> + return device_driver_attach(usb_generic_driver.drvwrap.driver, dev);
> + return error;
I think that's right. A little testing wouldn't hurt.
> Anything else in this patch series? I was concerned about the naming
> for "generic_init" in patch 2 ("subclass").
Yes; see the suggestions in
https://marc.info/?l=linux-usb&m=157063168632242&w=2
Also (I didn't notice this earlier), in patch 1/5 it's not necessary to
EXPORT the usb_generic_* routines. They don't get used in the subclass
driver, only in usbcore.
> If there's nothing, I'll test and respin the patchset with the above
> changes tomorrow.
Okay, good.
Alan Stern
