Re: patch bus_add_device-losing-an-error-return-from-the-probe-method.patch added to gregkh-2.6 tree

[Dmitry Torokhov]

On 4/4/06, Greg KH <gregkh@xxxxxxx> 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...
>


--
Dmitry
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