RE: [PATCH v2 1/6] Add ancillary bus support

["Ertman, David M" <david.m.ertman@intel.com>]

> -----Original Message-----
> From: Leon Romanovsky <leon@kernel.org>
> Sent: Tuesday, October 6, 2020 10:23 AM
> To: Ertman, David M <david.m.ertman@intel.com>
> Cc: alsa-devel@alsa-project.org; tiwai@suse.de; broonie@kernel.org; linux-
> rdma@vger.kernel.org; jgg@nvidia.com; dledford@redhat.com;
> netdev@vger.kernel.org; davem@davemloft.net; kuba@kernel.org;
> gregkh@linuxfoundation.org; ranjani.sridharan@linux.intel.com; pierre-
> louis.bossart@linux.intel.com; fred.oh@linux.intel.com;
> parav@mellanox.com; Saleem, Shiraz <shiraz.saleem@intel.com>; Williams,
> Dan J <dan.j.williams@intel.com>; Patil, Kiran <kiran.patil@intel.com>
> Subject: Re: [PATCH v2 1/6] Add ancillary bus support
> 
> On Mon, Oct 05, 2020 at 11:24:41AM -0700, Dave Ertman wrote:
> > Add support for the Ancillary Bus, ancillary_device and ancillary_driver.
> > It enables drivers to create an ancillary_device and bind an
> > ancillary_driver to it.
> >
> > The bus supports probe/remove shutdown and suspend/resume callbacks.
> > Each ancillary_device has a unique string based id; driver binds to
> > an ancillary_device based on this id through the bus.
> >
> > Co-developed-by: Kiran Patil <kiran.patil@intel.com>
> > Signed-off-by: Kiran Patil <kiran.patil@intel.com>
> > Co-developed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
> > Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
> > Co-developed-by: Fred Oh <fred.oh@linux.intel.com>
> > Signed-off-by: Fred Oh <fred.oh@linux.intel.com>
> > Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
> > Reviewed-by: Parav Pandit <parav@mellanox.com>
> > Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
> > ---
> 
> <...>
> 
> > +/**
> > + * __ancillary_driver_register - register a driver for ancillary bus devices
> > + * @ancildrv: ancillary_driver structure
> > + * @owner: owning module/driver
> > + */
> > +int __ancillary_driver_register(struct ancillary_driver *ancildrv, struct
> module *owner)
> > +{
> > +	if (WARN_ON(!ancildrv->probe) || WARN_ON(!ancildrv->remove)
> ||
> > +	    WARN_ON(!ancildrv->shutdown) || WARN_ON(!ancildrv-
> >id_table))
> > +		return -EINVAL;
> 
> In our driver ->shutdown is empty, it will be best if ancillary bus will
> do "if (->remove) ..->remove()" pattern.
>

Yes, looking it over, only the probe needs to mandatory.  I will change the others to the
conditional model, and adjust the WARN_ONs.

 
> > +
> > +	ancildrv->driver.owner = owner;
> > +	ancildrv->driver.bus = &ancillary_bus_type;
> > +	ancildrv->driver.probe = ancillary_probe_driver;
> > +	ancildrv->driver.remove = ancillary_remove_driver;
> > +	ancildrv->driver.shutdown = ancillary_shutdown_driver;
> > +
>
> I think that this part is wrong, probe/remove/shutdown functions should
> come from ancillary_bus_type. 

From checking other usage cases, this is the model that is used for probe, remove,
and shutdown in drivers.  Here is the example from Greybus.

int greybus_register_driver(struct greybus_driver *driver, struct module *owner,
                            const char *mod_name)
{
        int retval;

        if (greybus_disabled())
                return -ENODEV;

        driver->driver.bus = &greybus_bus_type;
        driver->driver.name = driver->name;
        driver->driver.probe = greybus_probe;
        driver->driver.remove = greybus_remove;
        driver->driver.owner = owner;
        driver->driver.mod_name = mod_name;


> You are overwriting private device_driver
> callbacks that makes impossible to make container_of of ancillary_driver
> to chain operations.
> 

I am sorry, you lost me here.  you cannot perform container_of on the callbacks
because they are pointers, but if you are referring to going from device_driver
to the auxiliary_driver, that is what happens in auxiliary_probe_driver in the
very beginning.

static int auxiliary_probe_driver(struct device *dev)
145 {
146         struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
147         struct auxiliary_device *auxdev = to_auxiliary_dev(dev);

Did I miss your meaning?

-DaveE

> > +	return driver_register(&ancildrv->driver);
> > +}
> > +EXPORT_SYMBOL_GPL(__ancillary_driver_register);
> 
> Thanks