linux-kernel - Re: [net-next PATCH v2 10/14] device property: Introduce fwnode_get

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Message-ID: <20201218060932.GD14594@lsv03152.swis.in-blr01.nxp.com>
Date:   Fri, 18 Dec 2020 11:39:32 +0530
From:   Calvin Johnson <calvin.johnson@....nxp.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Grant Likely <grant.likely@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Pieter Jansen Van Vuuren <pieter.jansenvv@...boosystems.io>,
        Jon <jon@...id-run.com>, linux.cj@...il.com,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Diana Madalina Craciun <diana.craciun@....com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [net-next PATCH v2 10/14] device property: Introduce
 fwnode_get_id()

Hi Laurent,

Thanks for reviewing.
On Tue, Dec 15, 2020 at 07:00:28PM +0200, Laurent Pinchart wrote:
> Hi Calvin,
> 
> Thank you for the patch.
> 
> On Tue, Dec 15, 2020 at 10:13:11PM +0530, Calvin Johnson wrote:
> > Using fwnode_get_id(), get the reg property value for DT node
> > and get the _ADR object value for ACPI node.
> > 
> > Signed-off-by: Calvin Johnson <calvin.johnson@....nxp.com>
> > ---
> > 
> > Changes in v2: None
> > 
> >  drivers/base/property.c  | 26 ++++++++++++++++++++++++++
> >  include/linux/property.h |  1 +
> >  2 files changed, 27 insertions(+)
> > 
> > diff --git a/drivers/base/property.c b/drivers/base/property.c
> > index 4c43d30145c6..1c50e17ae879 100644
> > --- a/drivers/base/property.c
> > +++ b/drivers/base/property.c
> > @@ -580,6 +580,32 @@ const char *fwnode_get_name_prefix(const struct fwnode_handle *fwnode)
> >  	return fwnode_call_ptr_op(fwnode, get_name_prefix);
> >  }
> >  
> > +/**
> > + * fwnode_get_id - Get the id of a fwnode.
> > + * @fwnode: firmware node
> > + * @id: id of the fwnode
> > + *
> 
> Is the concept of fwnode ID documented clearly somewhere ? I think this
> function should otherwise have more documentation, at least to explain
> what the ID is.

Agree. Will add more info here.
> 
> > + * Returns 0 on success or a negative errno.
> > + */
> > +int fwnode_get_id(struct fwnode_handle *fwnode, u32 *id)
> > +{
> > +	unsigned long long adr;
> > +	acpi_status status;
> > +
> > +	if (is_of_node(fwnode)) {
> > +		return of_property_read_u32(to_of_node(fwnode), "reg", id);
> > +	} else if (is_acpi_node(fwnode)) {
> > +		status = acpi_evaluate_integer(ACPI_HANDLE_FWNODE(fwnode),
> > +					       METHOD_NAME__ADR, NULL, &adr);
> > +		if (ACPI_FAILURE(status))
> > +			return -ENODATA;
> 
> Would it make sense to standardize error codes ? of_property_read_u32()
> can return -EINVAL, -ENODATA or -EOVERFLOW. I don't think the caller of
> this function would be very interested to tell those three cases apart.
> Maybe we should return -EINVAL in all error cases ? Or maybe different
> error codes to mean "the backend doesn't support the concept of IDs",
> and "the device doesn't have an ID" ?

I think it make sense to return just -EINVAL. Will take care in v3.

Thanks
Calvin