[PATCH v2 4/4] iio: Add OF support
Tomasz Figa
tomasz.figa at gmail.com
Mon Feb 4 10:14:52 EST 2013
On Sunday 03 of February 2013 19:55:47 Lars-Peter Clausen wrote:
> On 02/03/2013 06:30 PM, Tomasz Figa wrote:
> > On Sunday 03 of February 2013 09:01:07 Guenter Roeck wrote:
> >> On Sun, Feb 03, 2013 at 12:52:40PM +0100, Tomasz Figa wrote:
> >>> On Sunday 03 of February 2013 12:29:23 Lars-Peter Clausen wrote:
> >>>> On 02/03/2013 03:06 AM, Guenter Roeck wrote:
> >>>>> 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 ...
> >>>>
> >>>> A IIO trigger and a IIO device may have the same of_node, e.g. if
> >>>> they
> >>>> both belong to the same physical device. But you don't need to do
> >>>> the
> >>>> strcmp just compare dev->type to iio_dev_type i.e. dev->type ==
> >>>> &iio_dev_type. Although it doesn't really matter in practice first
> >>>> check for the of_node then check for the type, since the of_node
> >>>> will
> >>>> only match for a few devices at most, the type will match for quite
> >>>> a
> >>>> few.
> >>>
> >>> I must disagree.
> >>>
> >>> If you have two IIO devices provided by one physical device, then in
> >>>
> >>> device tree they should be represented as follows:
> >>> phys-dev at 12345678 {
> >>>
> >>> compatible = "some-physical-device";
> >>> /* ... */
> >>>
> >>> my_trig: iio-trigger {
> >>>
> >>> /* ... */
> >>>
> >>> };
> >>>
> >>> my_dev: iio-device {
> >>>
> >>> /* ... */
> >>>
> >>> };
> >>>
> >>> };
> >>>
> >>> Notice that phys-dev works here as an IIO bus on which its IIO
> >>> devices
> >>> are available. This is related to the convention that single OF
> >>> device node represents single device, which would be violated
> >>> otherwise.
> >>
> >> Right now the iio device is a child of the physical device, and I am
> >> simply passing of_node on to it. guess you are saying that is not
> >> correct ?
> >>
> >> If so, what would be the correct approach ? Something like the
> >> following ?
> >>
> >> voltage-sensor at 35 {
> >>
> >> compatible = "maxim,max1139";
> >> reg = <0x35>;
> >> vcc-supply = <®_3p3v>;
> >> vref-supply = <®_3p3v>;
> >>
> >> max1139-iio: iio-device {
> >>
> >> device_type = "iio_device";
> >> #io-channel-cells = <1>;
> >>
> >> };
> >>
> >> };
> >>
> >> and in the driver probe function:
> >> if (parent->of_node)
> >>
> >> iio_dev->dev.of_node = of_find_node_by_type(parent-
>of_node,
> >>
> >> "iio_device");
> >>
> >> Another option would be to use of_find_compatible_node() and
> >> something
> >> like compatible = "iio-device";
> >> in the iio-device node.
> >
> > A device node is defined as a node having compatible property. Other
> > nodes should be seen as helper nodes, which do not represent devices
> > (although they all have struct device_node in Linux).
> >
> > Also, AFAIK, device_type is a deprecated property used by some legacy
> > PowerPC machines and for current machines only compatible should be
> > used.
> >
> > So I guess the approach with compatible would be appropriate here.
> >
> > However for physical devices providing only a single IIO device it
> > might>
> > be better to allow simpler specification, like:
> > max1139-iio: voltage-sensor at 35 {
> >
> > compatible = "maxim,max1139", "iio_device";
>
> I don't think this makes a lot of sense. First of all iio_device an
> artificial Linux term, while the device tree should describe the
> hardware.
Well, if you look at an iio_device as a subdevice of a physical device
then it should make a bit more sense. (See nodes of GPIO/pinctrl pin banks
or regulators of a PMIC chip.)
> Secondly there is no generic iio driver which could match on
> a node with a "iio_device" compability string and stuff would just
> work. I mean we don't do
>
> compatible = "atmel,at91sam9260-i2c", "i2c-master";
>
> or similar either.
Right. We don't need the other compatible for simple devices with single
subdevice. This is implied by the driver registering a single IIO driver
using the node of physical device.
> > reg = <0x35>;
> > vcc-supply = <®_3p3v>;
> > vref-supply = <®_3p3v>;
> >
> > device_type = "iio_device";
Also we don't need this device_type. Basically we don't need to specify
whether given node is an iio_device or an iio_trigger. It's up to the
driver to register the node as a device or a trigger by setting dev.of_node
field properly.
So my suggestion would be to make the bindings as following. For single
subdevice:
voltage-sensor at 35 {
compatible = "maxim,max1139";
reg = <0x35>;
vcc-supply = <®_3p3v>;
vref-supply = <®_3p3v>;
#io-channel-cells = <1>;
};
For multiple subdevices:
voltage-sensor at 35 {
compatible = "maxim,max1139";
reg = <0x35>;
vcc-supply = <®_3p3v>;
vref-supply = <®_3p3v>;
subdevice1 {
/* Subdevice specific data */
#io-channel-cells = <1>;
};
subdevice2 {
/* Subdevice specific data */
#io-channel-cells = <1>;
}
};
Best regards,
Tomasz
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