On 29/03/16 10:44, Gregor Boirie wrote: > > > On 03/28/2016 05:03 PM, Jonathan Cameron wrote: > > [snip...] > >> >> Why is the sysfs interface specific to ak8975? >>>> AFAIK, this is just the first IIO driver implementation relying on floating >>>> point numbers. Should a single driver be enough to justify a "generic" API, >>>> I suppose code could be factored out in a similar way to over sampling rate >>>> support. People could call this on a per-driver basis. >>> Given it is an ABI, yes I think so. We don't want to end up with a >>> bunch of similar yet different interfaces. >>> >> Absolutely. Most interfaces get made up based on one implementation ;) >> A second is always nice, but here the interface is obvious enough we don't >> need to wait. > Right. I'll post a separate patch then. >>>>> Furthermore, why is it specific to magnetometer? Couldn't >>>>> accelerometers need the same thing? There's a thread discussing a >>>>> similar matrix on android-x86[1]. >>>> Same may apply to gyro / accelero / imu and magnetometers at least. >>>> inv_mpu_core.c already implements such a rotation matrix exposed as 3x3 integers >>>> array. Should we be smart enough to keep this compatible with existing userspace >>>> apps ? >>> You have to maintain the ABI. If both interfaces can co-exist, then >>> you can have both and mark the old one as deprecated. In time we can >>> remove the old one. >> If you want to (or someone else does) it would be good to add the new abi to >> inv_mpu_core as well and indeed mark the old one as deprecated. >> The cost of keeping it is negligible, so we may never actually bother to >> remove it. > What's the better way to mark this as deprecated ? dev_warn() ? __deprecated ? > Anything else ? Probably just documentation at this stage - anything else will be a pita for anyone using that driver. As long as it is clear in any docs + the code, which is the preferred option that's fine. I doubt we'll ever bother removing the old way. Jonathan >>>>>> diff --git a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt >>>>>> index 34a3206..f936f86 100644 >>>>>> --- a/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt >>>>>> +++ b/Documentation/devicetree/bindings/iio/magnetometer/ak8975.txt >>>>>> @@ -9,6 +9,7 @@ Optional properties: >>>>>> >>>>>> - gpios : should be device tree identifier of the magnetometer DRDY pin >>>>>> - vdd-supply: an optional regulator that needs to be on to provide VDD >>>>>> + - matrix: an optional 3x3 mounting rotation matrix >>>>> Perhaps "rotation-matrx" would be a better name in case there's ever >>>>> any other matrix needed. >>>> What about "mounting-matrix" ? >>> Sure. >> Works for me as well. >>> Rob >>> -- >>> 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
