On Tue, Feb 04, 2025 at 11:08:11AM +0100, Thomas Weißschuh wrote:
> On 2025-02-03 15:25:17+0100, Greg Kroah-Hartman wrote:
> > +static void faux_remove(struct device *dev)
> > +{
> > + struct faux_object *faux_obj = to_faux_object(dev);
> > + struct faux_device *faux_dev = &faux_obj->faux_dev;
> > + const struct faux_driver_ops *faux_ops = faux_obj->faux_ops;
> > +
> > + if (faux_ops && faux_ops->remove)
> > + faux_ops->remove(faux_dev);
> > +}
> > +
> > +static const struct bus_type faux_bus_type = {
> > + .name = "faux_bus",
>
> Is the _bus suffix intentional?
It was intentional.
> Other busses don't have it.
True. Naming is hard. I guess /sys/bus/faux/ makes sense, I will go
rename it.
But for the "root" device, does /sys/devices/faux_bus/ make sense, or
should it be /sys/devices/faux/ as well? I'm now leaning toward the
latter...
> > + .match = faux_match,
> > + .probe = faux_probe,
> > + .remove = faux_remove,
> > +};
> > +
> > +static void faux_device_release(struct device *dev)
> > +{
> > + struct faux_object *faux_obj = to_faux_object(dev);
> > + struct device_driver *drv = &faux_obj->driver;
> > +
> > + /*
> > + * Now that the device is going away, it has been unbound from the
> > + * driver we created for it, so it is safe to unregister the driver from
> > + * the system.
> > + */
> > + driver_unregister(drv);
> > +
> > + kfree(faux_obj);
> > +}
> > +
> > +/**
> > + * __faux_device_create - create and register a faux device and driver
> > + * @name: name of the device and driver we are adding
> > + * @faux_ops: struct faux_driver_ops that the new device will call back into, can be NULL
> > + * @owner: module owner of the device/driver
> > + *
> > + * Create a new faux device and driver, both with the same name, and register
> > + * them in the driver core properly. The probe() callback of @faux_ops will be
> > + * called with the new device that is created for the caller to do something
> > + * with.
> > + */
> > +struct faux_device *__faux_device_create(const char *name,
> > + struct faux_driver_ops *faux_ops,
>
> const
>
> > + struct module *owner)
>
> What about attributes?
What in-kernel user of this wants an attribute for such a device?
And again, if we find one, we can make a faux_device_create_groups()
call that takes a pointer to an attribute group structure if it's really
needed.
>
> > +{
> > + struct device_driver *drv;
> > + struct device *dev;
> > + struct faux_object *faux_obj;
> > + struct faux_device *faux_dev;
> > + int ret;
> > +
> > + faux_obj = kzalloc(sizeof(*faux_obj) + strlen(name) + 1, GFP_KERNEL);
> > + if (!faux_obj)
> > + return NULL;
> > +
> > + /* Save off the name of the object into local memory */
> > + strcpy(faux_obj->name, name);
> > +
> > + /* Initialize the driver portion and register it with the driver core */
> > + faux_obj->faux_ops = faux_ops;
> > + drv = &faux_obj->driver;
> > +
> > + drv->owner = owner;
> > + drv->name = faux_obj->name;
>
> Assuming most names are constant, this would be better with kstrdup_const().
> Which is also used by dev_set_name() under the hood.
I've now removed the additional driver, but note that this is just a
pointer assignment, which is fine to do here as the lifespan of
faux_obj->name outlived the driver structure's lifespan.
thanks for the review, much appreciated!
greg k-h
