Re: [RESEND PATCH v6 1/4] mfd: syscon: Add fwnode_to_regmap

[Dilip Kota]

On 4/17/2020 5:35 PM, Lee Jones wrote:
> On Mon, 06 Apr 2020, Dilip Kota wrote:
>
> > Traverse regmap handle entry from firmware node handle.
> >
> > Signed-off-by: Dilip Kota <eswara.kota@xxxxxxxxxxxxxxx>
> > ---
> > Changes on v5:
> >    No changes
> >    
> > Changes on v5:
> >    No changes
> >
> > Changes on v4:
> >    No changes
> >
> >   drivers/mfd/syscon.c       | 8 ++++++++
> >   include/linux/mfd/syscon.h | 6 ++++++
> >   2 files changed, 14 insertions(+)
> >
> > diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> > index 3a97816d0cba..e085c50816b9 100644
> > --- a/drivers/mfd/syscon.c
> > +++ b/drivers/mfd/syscon.c
> > @@ -178,6 +178,14 @@ struct regmap *device_node_to_regmap(struct device_node *np)
> >   }
> >   EXPORT_SYMBOL_GPL(device_node_to_regmap);
> >   
> > +struct regmap *fwnode_to_regmap(struct fwnode_handle *fwnode)
> > +{
> > +	struct device_node *np = to_of_node(fwnode);
> You are assuming that the fwnode was Device Tree pointer.
>
> The point of a fwnode is that it could be one of multiple types.
>
> What if it was a pointer to an ACPI property?
Yes, i missed to check in other perspective. Thanks for pointing it.
While going through the System control driver to address the query, i 
noticed that System Control
driver is talking with 'of' framework only. (No ACPI)

So, i think to add a defensive check and return error pointer if 
'to_of_node' returns NULL
As System control Driver cannot talk with ACPI, so fwnode_to_regmap() 
cannot talk and return error.

Or, the other option is removing the 'fwnode_to_regmap()' definition 
itself, to avoid confusion as fwnode can
point to 'OF', 'ACPI'or 'swnode'.

But, i feel return error for ACPI or oother, looks better because 
'device_node' has fwnode pointer. And provide description
in the header file, mentioning function is success for 'OF' and returns 
error for the rest.

Regards,
Dilip

>