[PATCH v2 4/4] iio: Add OF support
Jonathan Cameron
jic23 at kernel.org
Mon Feb 4 07:58:57 EST 2013
On 02/03/2013 06:55 PM, 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. 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.
Lars, what you say here doesn't cover one 'interesting' case.
An iio_device has one aspect in which it is not artificial. It represents
a group of channels that may be sampled at 'one instance' on a given device.
We do have devices out there (no drivers as yet) where it will make sense
to have multiple iio_device instances for one 'chip'. This is typically
where we have multiple sampling rates for the different devices within
a package. The mxs-lradc has 8 different 'slots' and any subset of channels
can be assigned to any device. So it may at some point be controlled
via a driver registering 8 iio_device instances.
Now this might justify child nodes for the iio_device. I'm really not
sure, but thought I'd throw it in there. Note it is probably only
really relevant when we have clients using the interrupt driven interface
rather than iio_hwmon and similar which use a polled read. Right now
the polled and interrupt driven consumer interfaces are mutually exclusive
Now arguably we only want to pull this trick of multiple iio devices to
simplify the core handling of these 'interesting' bits of hardware, but
it does have a real meaning in hardware none the less.
Just thought I'd confuse things even further ;)
Jonathan
>
>
>> reg = <0x35>;
>> vcc-supply = <®_3p3v>;
>> vref-supply = <®_3p3v>;
>> device_type = "iio_device";
>> #io-channel-cells = <1>;
>> };
>>
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