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?). 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
