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SubjectRe: patch bus_add_device-losing-an-error-return-from-the-probe-method.patch added to gregkh-2.6 tree
On 4/4/06, Greg KH <> wrote:
> Hm, no, I unwound this mess, and found the following:
> - bus_add_device() calls device_attach()
> - device_attach() calls bus_for_each_drv() for every driver on the bus
> - bus_for_each_drv() walks all drivers on the bus and calls
> __device_attach() for every individual driver
> - __device_attach() calls driver_probe_device() for that driver and device
> - driver_probe_device() calls down to the probe() function for the
> driver, passing it that driver, if match() for the bus matches this
> device.
> - if that probe() function returns -ENODEV or -ENXIO[1] then the error
> is ignored and 0 is returned, causing the loop to continue to try
> more drivers
> - if the probe() function returns any other error code, it is
> propagated up, all the way back to bus_add_device.

But why do we do that? probe() failing is driver's problem. The device
is still there and should still be presented in sysfs. I don't think
that we should stop if probe() fails - maybe next driver manages to
bind itself.

> - if the probe() function returns 0, the device is bound to the driver,
> and it returns 0. Hm, looks like we continue to loop here too, we
> could probably stop now that we have bound a driver to the device.

Could it be that logic is simply reversed?

> So, I'm pretty sure that this is safe and should work just fine. To be
> sure, let me go reboot my box with this change on it after I finish this
> email :)
> Does that help?
> thanks,
> greg k-h
> [1] - stupid agp drivers (or some other video drivers) require this. I
> need to go fix them up so they don't do this, if they haven't been
> fixed already...

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