On 02/03/2013 12:47 PM, Lars-Peter Clausen wrote: > On 02/03/2013 12:39 PM, Jonathan Cameron wrote: >> On 02/02/2013 04:10 PM, Guenter Roeck wrote: >>> On Sat, Feb 02, 2013 at 10:29:02AM +0000, Jonathan Cameron wrote: >>>> On 01/31/2013 09:43 PM, Guenter Roeck wrote: >>>>> Provide bindings, new API access functions, and parse OF data >>>>> during initialization. >>>>> >>>> Firstly thanks for working on this Guenter, it's been a big hole >>>> for a while largely because non of our largest developers were >>>> actually using development platforms with device tree support. >>>> >>>> Given my knowledge of device tree is based on the odd article >>>> and looking at similar sets of bindings this morning, my comments >>>> are likely to be somewhat superficial and uninformed ;) >>>> >>>> Mostly on this one I'll take a back seat and let those who >>>> know this stuff better come to a consensus. >>>> >>>> Jonathan >>>> >>>>> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx> >>>>> --- >>>>> .../devicetree/bindings/iio/iio-bindings.txt | 97 ++++++++ >>>>> drivers/iio/inkern.c | 241 ++++++++++++++++---- >>>>> include/linux/iio/consumer.h | 8 + >>>>> 3 files changed, 299 insertions(+), 47 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..0f51c95 >>>>> --- /dev/null >>>>> +++ b/Documentation/devicetree/bindings/iio/iio-bindings.txt >>>>> @@ -0,0 +1,97 @@ >>>>> +This binding is a work-in-progress, and are based on clock bindings and >>>>> +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 more 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. >>>>> + >>>>> +Optional properties: >>>>> +io-channel-output-names: >>>>> + Recommended to be a list of strings of IIO output signal >>>>> + names indexed by the first cell in the IIO specifier. >>>>> + However, the meaning of io-channel-output-names is domain >>>>> + specific to the IIO provider, and is only provided to >>>>> + encourage using the same meaning for the majority of IIO >>>>> + providers. This format may not work for IIO providers >>>>> + using a complex IIO specifier format. In those cases it >>>>> + is recommended to omit this property and create a binding >>>>> + specific names property. >>>>> + >>>>> + IIO consumer nodes must never directly reference >>>>> + the provider's io-channel-output-names property. >>>>> + >>>>> +For example: >>>>> + >>>>> + adc: adc@35 { >>>>> + compatible = "maxim,max1139"; >>>>> + reg = <0x35>; >>>>> + #io-channel-cells = <1>; >>>>> + io-channel-output-names = "adc1", "adc2"; >>>>> + }; >>>>> + >>>>> +- this node defines a device with two named IIO outputs, the first named >>>>> + "adc1" and the second named "adc2". Consumer nodes always reference >>>>> + IIO channels by index. The names should reflect the IIO output signal >>>>> + names for the device. >>>>> + >>>>> +==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@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"; >>>> Having different numbers of channels and channel names seems >>>> unusual... Deliberate or you got bored making up channel names? >>>> >>>> Why use indexed values for <&adc 0> etc rather than the output >>>> channel names on adc? For the iio_map stuff we initialy used >>>> indexes but got a lot of responses that it was a silly idea and >>>> naming was much more consistent and easy to follow. >>>> >>>> Is there a fundamental reason for it here? >>>> >>>> (note I don't mind either way as this seems more compact and cleaner >>>> in some ways) >>>> >>> >>> It follows the structure used by clocks, which uses the provided name(s) to >>> calculate an index into io-channels. This way, the provider does not have to >>> provide the mapping, the consumer does not have to know the io-channel index, >>> and the consumer code can call something like >>> >>> channel = iio_get_channel(dev, "vcc"); >>> >>> In the above example, "vcc" will map to "<&adc, 0>", and "vref" to "<&adc, 2>". >>> >>> This works for both platform data and OF data (though platform data will >>> still need provider-based mapping, at least for now). >>> >>> This lets the code use a static name (eg "vcc"), and the mapping to the actual >>> provider happens through devicetree. Since the name is only used locally and >>> consumer driver specific, there is no need to define globally unique names. >>> >>> With this approach, the io channel map is not needed at all for the OF case. >>> I had used it in this version of the patch set, but got rid of it now. >>> >>> Actually, provider based mapping doesn't even work. If the consumer is >>> instantiated before the provider, the mapping doesn't exist yet, and the >>> call to iio_channel_get_all will fail. There is no way to prevent this, >>> as providers can come online at any time and there is no means to enforce that >>> all providers are already active by the time the consumers are instantiated. >>> Even if a mapping exists, there is no way to know if it is complete, if a >>> consumer is mapped to multiple providers. >>> >>> With the consumer based mapping, iio_channel_get_all 'knows' that not all >>> requested providers are available and can return -EPROBEDEFER in that case. >> Thanks. That makes sense. At the moment iio_hwmon is the only case that >> does a 'get all'. Clearly things are easier when the driver is requesting a >> specific set and we can do the back off much more easily. >> >>> >>> As a side effect, we can also use the names - if provided - as channel >>> labels in iio_hwmon. >>> >>> Note this will require the iio_get_channel API to change from taking the >>> consumer device name to taking the consumer device pointer as argument. >>> This will enable it to work for both OF and non-OF cases, should address Lars' >>> concerns about duplicate API functions, and synchronize the code to match how >>> the clock framework works. >> >> Agreed, doing this gives us a cleaner syntax as well. Note there are other >> users of that function in tree so be sure to get them all! >> >>> >>> Thanks, >>> Guenter >> Thanks for the explanation. What I was actually suggesting was something >> like: >> >> adc: max1139@35 { >> compatible = "maxim,max1139"; >> reg = <0x35>; >> #io-channel-cells = <1>; >> io-channel-output-names = "adc1", "adc2", "adc3" >> }; >> >> iio_hwmon { >> compatible = "iio-hwmon"; >> io-channels = <&adc "adc1">, <&adc "adc2">, <&adc "adc3">, >> io-channel-names = "vcc", "vdd", "vref"; >> } >> >> Having taken a look at the available syntax, those <> pairs have >> to be unsigned integers? Hence the additional level of indirection? > > Yea, I think mixing phandles and strings simply doesn't work, due how > devicetree stores things. > Another possibility would beto do things the way the regulator framework does an have each channel as a subnode to the converter devices eg. adc: max1139@35 { compatible = "maxim,max1139"; reg = <0x35>; adc0: adc@0 { reg = <0>; }; adc1: adc@1 { reg = <1>; }; adc2: adc@2 { reg = <2>; }; }; iio_hwmon { compatible = "iio-hwmon"; io-channels = <&adc0>, <&adc1>, <&adc2>; io-channel-names = "vcc", "vdd", "vref"; }; But I'm not sure how much sense this makes for IIO. - Lars >> >> (sorry, I'm getting you to give me a tutorial on device tree syntax rather >> than the actual issue here!) >> >> I guess it was desirable to keep the syntax relatively simple but that occasionally >> adds the requirement for a bit of indirection. >> >> >> >> Jonathan > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
