Message-ID: <20130220181148.GA19278@roeck-us.net>
Date:	Wed, 20 Feb 2013 10:11:48 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Rob Herring <robherring2@...il.com>
Cc:	linux-iio@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Anton Vorontsov <cbou@...l.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	devicetree-discuss@...ts.ozlabs.org,
	Tomasz Figa <tomasz.figa@...il.com>,
	Rob Herring <rob.herring@...xeda.com>,
	linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>
Subject: Re: [PATCH v5] iio: Add OF support

On Wed, Feb 20, 2013 at 11:38:22AM -0600, Rob Herring wrote:
> On 02/07/2013 11:09 AM, Guenter Roeck wrote:
> > Provide bindings and parse OF data during initialization.
> > 
> > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > ---
> > v5:
> > - Updated examples in bindings.
> > v4:
> > - Fixed wrong parameter to dummy of_iio_channel_get_by_name if CONFIG_OF is
> >   undefined, and wrong return value.
> > - Initialize indio_dev->of_node in iio_device_register if the calling driver
> >   neglected to do it.
> > v3:
> > - Cleaned up documentation (formatting, left-over clock references)
> > - Updated bindings description to permit sub-devices
> > - When searching for iio devices, use the pointer to the iio device type instead
> >   of strcmp. Rename iio_dev_type to iio_device_type (to match other device
> >   types) and make it global for that purpose. Check the OF node first, then the
> >   device type, as the node is less likely to match.
> > - Move the common code in of_iio_channel_get and of_iio_channel_get_all to
> >   __of_iio_channel_get.
> > - Return NULL from of_iio_channel_get_by_name if nothing is found, or
> >   an error if there is a problem with consistency or if the provider device is
> >   not yet available.
> > - In iio_channel_get, return if of_iio_channel_get_by_name() returns a channel
> >   or an error, and continue otherwise.
> > v2:
> > - Rebased to iio/togreg
> > - Documentation update per feedback
> > - Dropped io-channel-output-names from the bindings document. The property is
> >   not used in the code, and it is not entirely clear what it would be used for.
> >   If there is a need for it, we can add it back in later on.
> > - Don't export OF specific API calls
> > - For OF support, no longer depend on iio_map
> > - Add #ifdef CONFIG_OF where appropriate, and ensure that the code still builds
> >   if it is not selected.
> > - Change iio_channel_get to take device pointer as argument instead of device
> >   name. Retain old API as of_iio_channel_get_sys.
> > - iio_channel_get now works for both OF and non-OF configurations
> > - Use regulator to get vref for max1363 driver.
> > 
> >  .../devicetree/bindings/iio/iio-bindings.txt       |   97 +++++++++++
> >  drivers/iio/iio_core.h                             |    1 +
> >  drivers/iio/industrialio-core.c                    |    8 +-
> >  drivers/iio/inkern.c                               |  171 ++++++++++++++++++++
> >  4 files changed, 275 insertions(+), 2 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/iio/iio-bindings.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/iio-bindings.txt b/Documentation/devicetree/bindings/iio/iio-bindings.txt
> > new file mode 100644
> > index 0000000..1182845
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/iio-bindings.txt
> > @@ -0,0 +1,97 @@
> > +This binding is a work-in-progress. It is derived from clock bindings,
> > +and based on suggestions from Lars-Peter Clausen [1].
> 
> Bindings are an ABI. It should not be a WIP. What part is a WIP?
> 
The text is copied from clock bindings. I do not claim to be better
than the clock subsystem is doing in respect to its bindings.

I'll be more than happy to take this text out if it is a source of contention,
even more so if that is what is holding up the patch. Jonathan ?

Thanks,
Guenter

> Knowing nothing about IIO, the binding seems sane.
> 
> Rob
> 
> > +Sources of IIO channels can be represented by any node in the device
> > +tree. Those nodes are designated as IIO providers. IIO consumer
> > +nodes use a phandle and IIO specifier pair to connect IIO provider
> > +outputs to IIO inputs. Similar to the gpio specifiers, an IIO
> > +specifier is an array of one or more cells identifying the IIO
> > +output on a device. The length of an IIO specifier is defined by the
> > +value of a #io-channel-cells property in the IIO provider node.
> > +
> > +[1] http://marc.info/?l=linux-iio&m=135902119507483&w=2
> > +
> > +==IIO providers==
> > +
> > +Required properties:
> > +#io-channel-cells: Number of cells in an IIO specifier; Typically 0 for nodes
> > +		   with a single IIO output and 1 for nodes with multiple
> > +		   IIO outputs.
> > +
> > +Example for a simple configuration with no trigger:
> > +
> > +	adc: voltage-sensor@35 {
> > +		compatible = "maxim,max1139";
> > +		reg = <0x35>;
> > +		#io-channel-cells = <1>;
> > +	};
> > +
> > +Example for a configuration with trigger:
> > +
> > +	adc@35 {
> > +		compatible = "some-vendor,some-adc";
> > +		reg = <0x35>;
> > +
> > +		adc1: iio-device@0 {
> > +			#io-channel-cells = <1>;
> > +			/* other properties */
> > +		};
> > +		adc2: iio-device@1 {
> > +			#io-channel-cells = <1>;
> > +			/* other properties */
> > +		};
> > +	};
> > +
> > +==IIO consumers==
> > +
> > +Required properties:
> > +io-channels:	List of phandle and IIO specifier pairs, one pair
> > +		for each IIO input to the device. Note: if the
> > +		IIO provider specifies '0' for #io-channel-cells,
> > +		then only the phandle portion of the pair will appear.
> > +
> > +Optional properties:
> > +io-channel-names:
> > +		List of IIO input name strings sorted in the same
> > +		order as the io-channels property. Consumers drivers
> > +		will use io-channel-names to match IIO input names
> > +		with IIO specifiers.
> > +io-channel-ranges:
> > +		Empty property indicating that child nodes can inherit named
> > +		IIO channels from this node. Useful for bus nodes to provide
> > +		and IIO channel to their children.
> > +
> > +For example:
> > +
> > +	device {
> > +		io-channels = <&adc 1>, <&ref 0>;
> > +		io-channel-names = "vcc", "vdd";
> > +	};
> > +
> > +This represents a device with two IIO inputs, named "vcc" and "vdd".
> > +The vcc channel is connected to output 1 of the &adc device, and the
> > +vdd channel is connected to output 0 of the &ref device.
> > +
> > +==Example==
> > +
> > +	adc: max1139@35 {
> > +		compatible = "maxim,max1139";
> > +		reg = <0x35>;
> > +		#io-channel-cells = <1>;
> > +	};
> > +
> > +	...
> > +
> > +	iio_hwmon {
> > +		compatible = "iio-hwmon";
> > +		io-channels = <&adc 0>, <&adc 1>, <&adc 2>,
> > +			<&adc 3>, <&adc 4>, <&adc 5>,
> > +			<&adc 6>, <&adc 7>, <&adc 8>,
> > +			<&adc 9>;
> > +	};
> > +
> > +	some_consumer {
> > +		compatible = "some-consumer";
> > +		io-channels = <&adc 10>, <&adc 11>;
> > +		io-channel-names = "adc1", "adc2";
> > +	};
> > diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> > index f652e6a..05c1b74 100644
> > --- a/drivers/iio/iio_core.h
> > +++ b/drivers/iio/iio_core.h
> > @@ -18,6 +18,7 @@
> >  struct iio_chan_spec;
> >  struct iio_dev;
> >  
> > +extern struct device_type iio_device_type;
> >  
> >  int __iio_add_chan_devattr(const char *postfix,
> >  			   struct iio_chan_spec const *chan,
> > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> > index 8848f16..6d8b027 100644
> > --- a/drivers/iio/industrialio-core.c
> > +++ b/drivers/iio/industrialio-core.c
> > @@ -847,7 +847,7 @@ static void iio_dev_release(struct device *device)
> >  	kfree(indio_dev);
> >  }
> >  
> > -static struct device_type iio_dev_type = {
> > +struct device_type iio_device_type = {
> >  	.name = "iio_device",
> >  	.release = iio_dev_release,
> >  };
> > @@ -869,7 +869,7 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
> >  
> >  	if (dev) {
> >  		dev->dev.groups = dev->groups;
> > -		dev->dev.type = &iio_dev_type;
> > +		dev->dev.type = &iio_device_type;
> >  		dev->dev.bus = &iio_bus_type;
> >  		device_initialize(&dev->dev);
> >  		dev_set_drvdata(&dev->dev, (void *)dev);
> > @@ -960,6 +960,10 @@ int iio_device_register(struct iio_dev *indio_dev)
> >  {
> >  	int ret;
> >  
> > +	/* If the calling driver did not initialize of_node, do it here */
> > +	if (!indio_dev->dev.of_node && indio_dev->dev.parent)
> > +		indio_dev->dev.of_node = indio_dev->dev.parent->of_node;
> > +
> >  	/* configure elements for the chrdev */
> >  	indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), indio_dev->id);
> >  
> > diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> > index b289915..795d100 100644
> > --- a/drivers/iio/inkern.c
> > +++ b/drivers/iio/inkern.c
> > @@ -10,6 +10,7 @@
> >  #include <linux/export.h>
> >  #include <linux/slab.h>
> >  #include <linux/mutex.h>
> > +#include <linux/of.h>
> >  
> >  #include <linux/iio/iio.h>
> >  #include "iio_core.h"
> > @@ -92,6 +93,164 @@ static const struct iio_chan_spec
> >  	return chan;
> >  }
> >  
> > +#ifdef CONFIG_OF
> > +
> > +static int iio_dev_node_match(struct device *dev, void *data)
> > +{
> > +	return dev->of_node == data && dev->type == &iio_device_type;
> > +}
> > +
> > +static int __of_iio_channel_get(struct iio_channel *channel,
> > +				struct device_node *np, int index)
> > +{
> > +	struct device *idev;
> > +	struct iio_dev *indio_dev;
> > +	int err;
> > +	struct of_phandle_args iiospec;
> > +
> > +	err = of_parse_phandle_with_args(np, "io-channels",
> > +					 "#io-channel-cells",
> > +					 index, &iiospec);
> > +	if (err)
> > +		return err;
> > +
> > +	idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
> > +			       iio_dev_node_match);
> > +	of_node_put(iiospec.np);
> > +	if (idev == NULL)
> > +		return -EPROBE_DEFER;
> > +
> > +	indio_dev = dev_to_iio_dev(idev);
> > +	channel->indio_dev = indio_dev;
> > +	index = iiospec.args_count ? iiospec.args[0] : 0;
> > +	if (index >= indio_dev->num_channels) {
> > +		return -EINVAL;
> > +		goto err_put;
> > +	}
> > +	channel->channel = &indio_dev->channels[index];
> > +
> > +	return 0;
> > +
> > +err_put:
> > +	iio_device_put(indio_dev);
> > +	return err;
> > +}
> > +
> > +static struct iio_channel *of_iio_channel_get(struct device_node *np, int index)
> > +{
> > +	struct iio_channel *channel;
> > +	int err;
> > +
> > +	if (index < 0)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
> > +	if (channel == NULL)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	err = __of_iio_channel_get(channel, np, index);
> > +	if (err)
> > +		goto err_free_channel;
> > +
> > +	return channel;
> > +
> > +err_free_channel:
> > +	kfree(channel);
> > +	return ERR_PTR(err);
> > +}
> > +
> > +static struct iio_channel *of_iio_channel_get_by_name(struct device_node *np,
> > +						      const char *name)
> > +{
> > +	struct iio_channel *chan = NULL;
> > +
> > +	/* Walk up the tree of devices looking for a matching iio channel */
> > +	while (np) {
> > +		int index = 0;
> > +
> > +		/*
> > +		 * For named iio channels, first look up the name in the
> > +		 * "io-channel-names" property.  If it cannot be found, the
> > +		 * index will be an error code, and of_iio_channel_get()
> > +		 * will fail.
> > +		 */
> > +		if (name)
> > +			index = of_property_match_string(np, "io-channel-names",
> > +							 name);
> > +		chan = of_iio_channel_get(np, index);
> > +		if (!IS_ERR(chan))
> > +			break;
> > +		else if (name && index >= 0) {
> > +			pr_err("ERROR: could not get IIO channel %s:%s(%i)\n",
> > +				np->full_name, name ? name : "", index);
> > +			return chan;
> > +		}
> > +
> > +		/*
> > +		 * No matching IIO channel found on this node.
> > +		 * If the parent node has a "io-channel-ranges" property,
> > +		 * then we can try one of its channels.
> > +		 */
> > +		np = np->parent;
> > +		if (np && !of_get_property(np, "io-channel-ranges", NULL))
> > +			break;
> > +	}
> > +	return chan;
> > +}
> > +
> > +static struct iio_channel *of_iio_channel_get_all(struct device *dev)
> > +{
> > +	struct iio_channel *chans;
> > +	int i, mapind, nummaps = 0;
> > +	int ret;
> > +
> > +	do {
> > +		ret = of_parse_phandle_with_args(dev->of_node,
> > +						 "io-channels",
> > +						 "#io-channel-cells",
> > +						 nummaps, NULL);
> > +		if (ret < 0)
> > +			break;
> > +	} while (++nummaps);
> > +
> > +	if (nummaps == 0)	/* no error, return NULL to search map table */
> > +		return NULL;
> > +
> > +	/* NULL terminated array to save passing size */
> > +	chans = kcalloc(nummaps + 1, sizeof(*chans), GFP_KERNEL);
> > +	if (chans == NULL)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	/* Search for OF matches */
> > +	for (mapind = 0; mapind < nummaps; mapind++) {
> > +		ret = __of_iio_channel_get(&chans[mapind], dev->of_node,
> > +					   mapind);
> > +		if (ret)
> > +			goto error_free_chans;
> > +	}
> > +	return chans;
> > +
> > +error_free_chans:
> > +	for (i = 0; i < mapind; i++)
> > +		iio_device_put(chans[i].indio_dev);
> > +	kfree(chans);
> > +	return ERR_PTR(ret);
> > +}
> > +
> > +#else /* CONFIG_OF */
> > +
> > +static inline struct iio_channel *
> > +of_iio_channel_get_by_name(struct device_node *np, const char *name)
> > +{
> > +	return NULL;
> > +}
> > +
> > +static inline struct iio_channel *of_iio_channel_get_all(struct device *dev)
> > +{
> > +	return NULL;
> > +}
> > +
> > +#endif /* CONFIG_OF */
> >  
> >  static struct iio_channel *iio_channel_get_sys(const char *name,
> >  					       const char *channel_name)
> > @@ -150,7 +309,14 @@ struct iio_channel *iio_channel_get(struct device *dev,
> >  				    const char *channel_name)
> >  {
> >  	const char *name = dev ? dev_name(dev) : NULL;
> > +	struct iio_channel *channel;
> >  
> > +	if (dev) {
> > +		channel = of_iio_channel_get_by_name(dev->of_node,
> > +						     channel_name);
> > +		if (channel != NULL)
> > +			return channel;
> > +	}
> >  	return iio_channel_get_sys(name, channel_name);
> >  }
> >  EXPORT_SYMBOL_GPL(iio_channel_get);
> > @@ -173,6 +339,11 @@ struct iio_channel *iio_channel_get_all(struct device *dev)
> >  
> >  	if (dev == NULL)
> >  		return ERR_PTR(-EINVAL);
> > +
> > +	chans = of_iio_channel_get_all(dev);
> > +	if (chans)
> > +		return chans;
> > +
> >  	name = dev_name(dev);
> >  
> >  	mutex_lock(&iio_map_list_lock);
> > 
> 
> 
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