linux-kernel - Re: [RFC PATCH 46/57] driver: Add variants of driver_find

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Date:   Tue, 4 Jun 2019 10:46:42 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-kernel@...r.kernel.org, rafael@...nel.org
Subject: Re: [RFC PATCH 46/57] driver: Add variants of driver_find_device()

On Tue, Jun 04, 2019 at 09:36:08AM +0100, Suzuki K Poulose wrote:
> 
> 
> On 03/06/2019 20:11, Greg KH wrote:
> > On Mon, Jun 03, 2019 at 04:50:12PM +0100, Suzuki K Poulose wrote:
> > > Add a wrappers to lookup a device by name for a given driver, by various
> > > generic properties of a device. This can avoid the proliferation of custom
> > > match functions throughout the drivers.
> > > 
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> > > ---
> > >   include/linux/device.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 44 insertions(+)
> > > 
> > > diff --git a/include/linux/device.h b/include/linux/device.h
> > > index 52d59d5..68d6e04 100644
> > > --- a/include/linux/device.h
> > > +++ b/include/linux/device.h
> > > @@ -401,6 +401,50 @@ struct device *driver_find_device(struct device_driver *drv,
> > >   				  struct device *start, void *data,
> > >   				  int (*match)(struct device *dev, const void *data));
> > > +/**
> > > + * driver_find_device_by_name - device iterator for locating a particular device
> > > + * of a specific name.
> > > + * @driver: the driver we're iterating
> > > + * @start: Device to begin with
> > > + * @name: name of the device to match
> > > + */
> > > +static inline struct device *driver_find_device_by_name(struct device_driver *drv,
> > > +							struct device *start,
> > > +							const char *name)
> > > +{
> > > +	return driver_find_device(drv, start, (void *)name, device_match_name);
> > 
> > Why is the cast needed?
> > 
> > > +}
> > > +
> > > +/**
> > > + * driver_find_device_by_of_node- device iterator for locating a particular device
> > > + * by of_node pointer.
> > > + * @driver: the driver we're iterating
> > > + * @start: Device to begin with
> > > + * @np: of_node pointer to match.
> > > + */
> > > +static inline struct device *
> > > +driver_find_device_by_of_node(struct device_driver *drv,
> > > +			      struct device *start,
> > > +			      const struct device_node *np)
> > > +{
> > > +	return driver_find_device(drv, start, (void *)np, device_match_of_node);
> > 
> > Same here.
> > 
> > > +}
> > > +
> > > +/**
> > > + * driver_find_device_by_fwnode- device iterator for locating a particular device
> > > + * by fwnode pointer.
> > > + * @driver: the driver we're iterating
> > > + * @start: Device to begin with
> > > + * @fwnode: fwnode pointer to match.
> > > + */
> > > +static inline struct device *
> > > +driver_find_device_by_fwnode(struct device_driver *drv,
> > > +			     struct device *start,
> > > +			     const struct fwnode_handle *fwnode)
> > > +{
> > > +	return driver_find_device(drv, start, (void *)fwnode, device_match_fwnode);
> > 
> > And here
> 
> Because the driver_find_device() expects a "void *" and not a "const void *".

Can we fix that?

> May be we could promote that to "const void *" in the core API too, since we
> have converted the "match" to const void * already. Thoughts ?

Yes, let's fix the core if possible.

thanks,

greg k-h