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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 Tue, Apr 04, 2006 at 02:00:48PM -0700, Greg KH wrote:
    > On Tue, Apr 04, 2006 at 04:23:43PM -0400, Dmitry Torokhov wrote:
    > > On 4/4/06, gregkh@suse.de <gregkh@suse.de> wrote:
    > > >
    > > > --- gregkh-2.6.orig/drivers/base/bus.c
    > > > +++ gregkh-2.6/drivers/base/bus.c
    > > > @@ -372,14 +372,17 @@ int bus_add_device(struct device * dev)
    > > >
    > > > if (bus) {
    > > > pr_debug("bus %s: add device %s\n", bus->name, dev->bus_id);
    > > > - device_attach(dev);
    > > > + error = device_attach(dev);
    > > > + if (error < 0)
    > > > + goto exit;
    > >
    > > I do not believe that this is correct. The fact that _some_ driver
    > > failed to attach to a device does not necessarily mean that device
    > > itself does not exist. While this assuption might work for platform
    > > devices it won't work for other busses.
    >
    > 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.
    > - 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.
    >
    > 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 :)

    Yup, things still seem to work properly for me. The patch will show up
    in the next -mm for others to beat on...

    thanks,

    greg k-h
    -
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