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

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Message-ID: <X9jrrMJIj2EQBykI@pendragon.ideasonboard.com>
Date:   Tue, 15 Dec 2020 19:00:28 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Calvin Johnson <calvin.johnson@....nxp.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 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.

> + * 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" ?

> +		*id = (u32)adr;
> +		return 0;
> +	}
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(fwnode_get_id);
> +
>  /**
>   * fwnode_get_parent - Return parent firwmare node
>   * @fwnode: Firmware whose parent is retrieved
> diff --git a/include/linux/property.h b/include/linux/property.h
> index 2d4542629d80..92d405cf2b07 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -82,6 +82,7 @@ struct fwnode_handle *fwnode_find_reference(const struct fwnode_handle *fwnode,
>  
>  const char *fwnode_get_name(const struct fwnode_handle *fwnode);
>  const char *fwnode_get_name_prefix(const struct fwnode_handle *fwnode);
> +int fwnode_get_id(struct fwnode_handle *fwnode, u32 *id);
>  struct fwnode_handle *fwnode_get_parent(const struct fwnode_handle *fwnode);
>  struct fwnode_handle *fwnode_get_next_parent(
>  	struct fwnode_handle *fwnode);

-- 
Regards,

Laurent Pinchart