linux-kernel - Re: [RESEND PATCH v2 1/2] device property: Add function to search for named child of device

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Date:	Fri, 10 Jun 2016 01:11:06 +0200
From:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:	Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
	Jaroslav Kysela <perex@...ex.cz>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Takashi Iwai <tiwai@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Robert Moore <robert.moore@...el.com>,
	Lv Zheng <lv.zheng@...el.com>, Len Brown <lenb@...nel.org>,
	alsa-devel@...a-project.org, linux-acpi@...r.kernel.org,
	devel@...ica.org, linux-kernel@...r.kernel.org,
	Support Opensource <support.opensource@...semi.com>,
	Sathyanarayana Nujella <sathyanarayana.nujella@...el.com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RESEND PATCH v2 1/2] device property: Add function to search for
 named child of device

On 6/9/2016 5:13 PM, Adam Thomson wrote:
> For device nodes in both DT and ACPI, it possible to have named
> child nodes which contain properties (an existing example being
> gpio-leds). This adds a function to find a named child node for
> a device which can be used by drivers for property retrieval.
>
> For ACPI data node name matching, a helper function is also added
> which returns false if CONFIG_ACPI is not set, otherwise it
> performs a string comparison on the data node name. This avoids
> using the acpi_data_node struct for non CONFIG_ACPI builds,
> which would otherwise cause a build failure.
>
> Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>
> Tested-by: Sathyanarayana Nujella <sathyanarayana.nujella@...el.com>

For some reason that didn't make it into the linux-acpi list, or at 
least I can't see it there.

> ---
>
> Changes in v2:
>   - Rebase to v4.7-rc1
>
>   drivers/base/property.c  | 28 ++++++++++++++++++++++++++++
>   include/acpi/acpi_bus.h  |  7 +++++++
>   include/linux/acpi.h     |  6 ++++++
>   include/linux/property.h |  3 +++
>   4 files changed, 44 insertions(+)
>
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index f38c21d..573b361 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -888,6 +888,34 @@ struct fwnode_handle *device_get_next_child_node(struct device *dev,
>   EXPORT_SYMBOL_GPL(device_get_next_child_node);
>
>   /**
> + * device_get_named_child_node - Return first matching named child node handle
> + * @dev: Device to find the named child node for.
> + * @childname: String to match child node name against.
> + */
> +struct fwnode_handle *device_get_named_child_node(struct device *dev,
> +						  const char *childname)
> +{
> +	struct fwnode_handle *child;
> +
> +	/*
> +	 * Find first matching named child node of this device.
> +	 * For ACPI this will be a data only sub-node.
> +	 */
> +	device_for_each_child_node(dev, child) {
> +		if (is_of_node(child)) {
> +			if (!strcasecmp(to_of_node(child)->name, childname))

Why do you use strcasecmp() here?

> +				return child;
> +		} else if (is_acpi_data_node(child)) {
> +			if (acpi_data_node_match(child, childname))
> +				return child;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(device_get_named_child_node);
> +
> +/**
>    * fwnode_handle_put - Drop reference to a device node
>    * @fwnode: Pointer to the device node to drop the reference to.
>    *
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 788c6c3..993bdd0 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -420,6 +420,13 @@ static inline struct acpi_data_node *to_acpi_data_node(struct fwnode_handle *fwn
>   		container_of(fwnode, struct acpi_data_node, fwnode) : NULL;
>   }
>
> +static inline bool acpi_data_node_match(struct fwnode_handle *fwnode,
> +					const char *name)
> +{
> +	return is_acpi_data_node(fwnode) ?
> +		(!strcasecmp(to_acpi_data_node(fwnode)->name, name)) : false;
> +}

Is there any particular reason to introduce this function instead of 
doing the test in device_get_named_child_node() directly?

> +
>   static inline struct fwnode_handle *acpi_fwnode_handle(struct acpi_device *adev)
>   {
>   	return &adev->fwnode;
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 288fac5..03039c4 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -568,6 +568,12 @@ static inline struct acpi_data_node *to_acpi_data_node(struct fwnode_handle *fwn
>   	return NULL;
>   }
>
> +static inline bool acpi_data_node_match(struct fwnode_handle *fwnode,
> +					const char *name)
> +{
> +	return false;
> +}
> +
>   static inline struct fwnode_handle *acpi_fwnode_handle(struct acpi_device *adev)
>   {
>   	return NULL;
> diff --git a/include/linux/property.h b/include/linux/property.h
> index ecab11e..3a2f9ae 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -77,6 +77,9 @@ struct fwnode_handle *device_get_next_child_node(struct device *dev,
>   	for (child = device_get_next_child_node(dev, NULL); child;	\
>   	     child = device_get_next_child_node(dev, child))
>
> +struct fwnode_handle *device_get_named_child_node(struct device *dev,
> +						  const char *childname);
> +
>   void fwnode_handle_put(struct fwnode_handle *fwnode);
>
>   unsigned int device_get_child_node_count(struct device *dev);
> --

Mika, Heikki, Andy, any feedback on this one?