[PATCH v2 4/4] iio: Add OF support
Guenter Roeck
linux at roeck-us.net
Sun Feb 3 13:06:51 EST 2013
On Sun, Feb 03, 2013 at 02:30:24AM +0100, Tomasz Figa wrote:
> Hi Guenter,
>
> Some comments inline.
>
> On Saturday 02 of February 2013 16:59:40 Guenter Roeck wrote:
> > Provide bindings and parse OF data during initialization.
> >
> > Signed-off-by: Guenter Roeck <linux at roeck-us.net>
> > ---
> > - 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.
> >
> > .../devicetree/bindings/iio/iio-bindings.txt | 76 ++++++++
> > drivers/iio/inkern.c | 186
> > ++++++++++++++++++++ 2 files changed, 262 insertions(+)
> > 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..58df5f6
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/iio-bindings.txt
> > @@ -0,0 +1,76 @@
> > +This binding is a work-in-progress. It is derived from clock bindings,
> > +and based on suggestions from Lars-Peter Clausen [1].
> > +
> > +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 clock 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.
> > +
> > +For example:
> > +
> > + adc: adc at 35 {
> > + compatible = "maxim,max1139";
> > + reg = <0x35>;
> > + #io-channel-cells = <1>;
> > + };
> > +
> > +==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 #clock-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 at 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>, <&adc 10>, <&adc 11>;
> > + io-channel-names = "vcc", "vdd", "vref", "1.2V";
> > + };
> > diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> > index b289915..d48f2a8 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 +93,179 @@ static const struct iio_chan_spec
> > return chan;
> > }
> >
> > +#ifdef CONFIG_OF
> > +
> > +static int iio_dev_node_match(struct device *dev, void *data)
> > +{
> > + return !strcmp(dev->type->name, "iio_device") && dev->of_node ==
> data;
>
> Hmm, do you need to check type name here? One device node should rather
> represent only one device, making node an unique identifier.
>
> It this is meant to be a sanity check, it could be done one time after
> finding the device.
>
Hi Tomasz,
This is what Lars had suggested earlier:
> Yes, use bus_find_device on iio_bus_type. A nice example how to use this to
> lookup device by of node is of_find_i2c_device_by_node. For IIO you also need
> to make sure that dev->type is iio_dev_type, since both devices and triggers
> are registered on the same bus.
Is it really needed, or in other words would it be sufficient to check if
of_node and data match each other ? Your reasoning makes sense to me, and I had
thought about it as well, but I don't really know, and I don't know how I could
test it and guarantee correctness either. I'll be happy to take the strcmp() out
if someone tells me that it is definitely not needed ...
> > +}
> > +
> > +static struct iio_channel *of_iio_channel_get(struct device_node *np,
> > int index) +{
> > + struct iio_channel *channel;
> > + struct device *idev;
> > + struct iio_dev *indio_dev;
> > + int err;
> > + struct of_phandle_args iiospec;
> > +
> > + if (index < 0)
> > + return ERR_PTR(-EINVAL);
> > +
> > + err = of_parse_phandle_with_args(np, "io-channels",
> > + "#io-channel-cells",
> > + index, &iiospec);
> > + if (err)
> > + return ERR_PTR(err);
> > +
> > + idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
> > + iio_dev_node_match);
> > + of_node_put(iiospec.np);
> > + if (idev == NULL)
> > + return ERR_PTR(-EPROBE_DEFER);
> > +
> > + indio_dev = dev_to_iio_dev(idev);
> > +
> > + channel = kzalloc(sizeof(*channel), GFP_KERNEL);
> > + if (channel == NULL) {
> > + err = -ENOMEM;
> > + goto err_no_mem;
> > + }
> > +
> > + channel->indio_dev = indio_dev;
> > + index = iiospec.args_count ? iiospec.args[0] : 0;
>
> What happens here with remaining phandle arguments?
>
> I'm not sure if such use case is needed for iio, but other subsystems give
> the possibility of specifying custom xlate callback translating from a
> custom specifier into channel number. (e.g. drivers/gpio/gpiolib-of.c)
>
I don't have a use case, and I hesitate to implement something that may
never be used (and I can not really test it either). And without a use
case we would not even know if the implementation makes sense or not.
It should be possible to add additional functionality later if needed.
Thanks,
Guenter
> Best regards,
> Tomasz
>
> > + if (index >= indio_dev->num_channels) {
> > + err = -EINVAL;
> > + goto err_no_channel;
> > + }
> > + channel->channel = &indio_dev->channels[index];
> > +
> > + return channel;
> > +
> > +err_no_channel:
> > + kfree(channel);
> > +err_no_mem:
> > + iio_device_put(indio_dev);
> > + 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 = ERR_PTR(-ENOENT);
> > +
> > + /* 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 = kzalloc(sizeof(*chans)*(nummaps + 1), GFP_KERNEL);
> > + if (chans == NULL) {
> > + ret = -ENOMEM;
> > + goto error;
> > + }
> > +
> > + /* Search for OF matches */
> > + for (mapind = 0; mapind < nummaps; mapind++) {
> > + struct device *idev;
> > + struct iio_dev *indio_dev;
> > + int channel;
> > + struct of_phandle_args iiospec;
> > +
> > + ret = of_parse_phandle_with_args(dev->of_node,
> > + "io-channels",
> > + "#io-channel-cells",
> > + mapind, &iiospec);
> > + if (ret)
> > + goto error_free_chans;
> > +
> > + idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
> > + iio_dev_node_match);
> > + of_node_put(iiospec.np);
> > + if (idev == NULL) {
> > + ret = -EPROBE_DEFER;
> > + goto error_free_chans;
> > + }
> > + indio_dev = dev_to_iio_dev(idev);
> > + channel = iiospec.args_count ? iiospec.args[0] : 0;
> > + if (channel >= indio_dev->num_channels) {
> > + ret = -EINVAL;
> > + goto error_free_chans;
> > + }
> > + chans[mapind].indio_dev = indio_dev;
> > + chans[mapind].channel = &indio_dev->channels[channel];
> > + }
> > + return chans;
> > +
> > +error_free_chans:
> > + for (i = 0; i < mapind; i++)
> > + iio_device_put(chans[i].indio_dev);
> > + kfree(chans);
> > +error:
> > + 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 ERR_PTR(-ENOENT);
> > +}
> > +
> > +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 +324,14 @@ 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 (!IS_ERR(channel))
> > + return channel;
> > + }
> > return iio_channel_get_sys(name, channel_name);
> > }
> > EXPORT_SYMBOL_GPL(iio_channel_get);
> > @@ -173,6 +354,11 @@ 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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