> On Sat, 2 Apr 2022 12:09:30 +0200 > Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote: > > > Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> > Hi Lorenzo, > > This runs in to the same feedback that was recently had for > https://lore.kernel.org/all/?q=Add+support+for+ICM-20608-D > but in a more extreme sense as this one presents the same whoami value > as for other sensors already supported. Things are made more > fun by the fact that sensors with the same WAI seem to have different > features (presence or not of a sensor hub - is there any documented > way to detect that?). Hi Jonathan, if we consider only the features implemented in st_lsm6dsx, asm330lhhx will be 1:1 compatible with lsm6dsr or lsm6dso, so we can just use one of bindings in this section to support it (the only side effect is it will be listed as "lsm6dsr" or "lsm6dso", but I guess it is ok). Agree? The only difference between asm330lhhx and asm330lhh is the former supports sensor-hub while the latter does not declare it (even if the use the same whoami). AFAIK there is no way to autodetect if the sensor supports sensor-hub and we can just try to discover slave devices connected. This can have some downside as described in the commit: commit 35619155d044830357f06f1d2c8188c4530b4d7a Author: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> Date: Sat Nov 13 16:23:14 2021 +0100 iio: imu: st_lsm6dsx: add dts property to disable sensor-hub I would like to merge the sections in st_lsm6dsx_settings struct for lsm6dsr, lsm6dso.. and lsm6dsop, asm330lhh since the only difference is sensor-hub support. I guess we can have 2 option here to avoid any sensor-hub corner cases: - provide the "st,disable-sensor-hub" in dts to disable sensor-hub for asm330lhh, lsm6dsop (need user changes) - add a bool variable st_lsm6dsx_settings[].id[] in order to specify if the chip supports sensor-hub. Which one do you prefer? Regards, Lorenzo > > As such, we should really be listing this as compatible with one > of the parts that is already supported such as the > LSM6DSR. > > For that we'll need a slightly more complex binding and it would > have the side effect that if the match was on that compatible we > would list the name as whatever that part is. > > I'm not sure that really matters a great deal, but it could in theory > create a userspace ABI change if we later needed to add explicit support > for the part due to some real differences not indicated by the WAI value. > > An extension is whether we should relax the need to match on WAI if > the part is considered compatible. I guess that depends on just how > compatible we think they are. > > So I see several steps to this process. > > 1) Add fallback compatibles for existing entries to first one with same WAI and > same feature set. > 2) Add fallback compatibles beyond that to first part introduced with particular > characteristics. For this we'd also want to have the driver relax its > handling to just warn if the WAI isn't listed for any of the parts that > share a particular set of characteristic (so you'll have to loop over the local > array again to check): > https://elixir.bootlin.com/linux/latest/source/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c#L1197 > Same argument applies as for the mpu6050 that, whilst we should modify that code to > cope, it's not a prerequisit for adding the compatible fallback to the binding. > Personally I'd like it to be the first patch in the series that modifies the > binding though. Note it'll be easy to add the fallbacks for this new part as > no mainline trees presumably use it. To 'fix' the rest we'll have to find > and update any DTs in mainline. > > Note this won't stop us needing to add compatibles to newer kernels (at very > least to the dt-binding, but probably also the driver), but it should help a newer > DT 'work' with an old kernel. > > Jonathan > > > > --- > > Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml b/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml > > index 0750f700a143..23637c420d20 100644 > > --- a/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml > > +++ b/Documentation/devicetree/bindings/iio/imu/st,lsm6dsx.yaml > > @@ -31,6 +31,7 @@ properties: > > - st,lsm6dsrx > > - st,lsm6dst > > - st,lsm6dsop > > + - st,asm330lhhx > > > > reg: > > maxItems: 1 >
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