Re: [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jun 08, 2021 at 07:07:49AM +0100, Christoph Hellwig wrote:
> > index 36d0c654ea6124..03591f82251302 100644
> > +++ b/drivers/base/bus.c
> > @@ -212,13 +212,9 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
> >  	dev = bus_find_device_by_name(bus, NULL, buf);
> >  	if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
> >  		err = device_driver_attach(drv, dev);
> > -
> > -		if (err > 0) {
> > +		if (!err) {
> >  			/* success */
> >  			err = count;
> > -		} else if (err == 0) {
> > -			/* driver didn't accept device */
> > -			err = -ENODEV;
> >  		}
> >  	}
> 
> I think we can also drop the dev->driver == NULL check above given
> that device_driver_attach covers it now.

I'm glad you noticed this because it is wonky today:

static ssize_t bind_store() {
        int err = -ENODEV;

        if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
               err = device_driver_attach() {
                    int ret = 0;
                    __device_driver_lock(dev, dev->parent);
                    if (!dev->p->dead && !dev->driver)
                           ..
                    return ret;
               }
        }
        return err;

Thus if dev->driver == NULL this will usually return -ENODEV unless it
races just right and returns 0. So I fixed it up to always return
-EBUSY and always read dev->driver under the lock.

Jason