On 05/21/2018 09:12 PM, Hans de Goede wrote: > Hi, > > On 21-05-18 17:07, Lars-Peter Clausen wrote: >> On 05/21/2018 03:44 PM, Hans de Goede wrote: >>> Hi, >>> >>> On 21-05-18 15:40, Hans de Goede wrote: >>>> Hi, >>>> >>>> On 21-05-18 15:31, Lars-Peter Clausen wrote: >>>>> On 05/21/2018 03:13 PM, Andy Shevchenko wrote: >>>>>> On Mon, 2018-05-21 at 14:34 +0200, Hans de Goede wrote: >>>>>>> On 21-05-18 11:19, Andy Shevchenko wrote: >>>>>> >>>>>>>>> Patches 6-9 use the new functionality creating one i2c-client per >>>>>>>>> I2cSerialBusV2 resource to make the sensor cluster on the HP X2 >>>>>>>>> work >>>>>>>>> and >>>>>>>>> are posted as part of this series to show how this functionality >>>>>>>>> can >>>>>>>>> be >>>>>>>>> used. >>>>>>>> >>>>>>>> I suppose it's better to do an "MFD" type of IIO driver for that >>>>>>>> chip. >>>>>>>> Check, for example, drivers/iio/imu/bmi160/bmi160_core.c >>>>>>> >>>>>>> That seems to be a single chip listening on a single i2c address / spi >>>>>>> chip-select. >>>>>> >>>>>> Ooops, wrong reference. >>>>>> >>>>>>> In the BSG1160 case the 3 sensors are listening on 3 different i2c >>>>>>> addresses. >>>>>> >>>>>> There is a Bosh magnetometer + accelerometer chip (BMC150). We have just >>>>>> two independent drivers for them. Luckily for ACPI they have different >>>>>> IDs (on the platforms where it's used like that). >>>>>> >>>>>> So, my series targeting the series of same IPs under one device... >>>>>> >>>>>>> We could use the drivers/mfd framework, but the we get platform >>>>>>> devices >>>>>>> and we would need to patch all 3 existing drivers to support platform >>>>>>> bindings and get a regmap from there (converting them to regmap where >>>>>>> necessary). >>>>>> >>>>>> ...and in your case MFD sounds better. Though why do you need to have a >>>>>> common regmap? >>>>> >>>>> I'm not convinced MFD is the right place. You wouldn't really utilize >>>>> anything of the MFD subsystem. And in a sense it is not a multi-function >>>>> device. It's just multiple devices that are described by the same firmware >>>>> description table entry. >>>>> >>>>> But I think some kind of board driver might be useful here that translates >>>>> the ACPI description into something more reasonable. I.e. bind to the ACPI >>>>> ID and then instantiate the 3 child I2C devices on the same bus. Those do >>>>> not have to be platform drivers and you do not have to use regmap. >>>>> >>>>> The current approach adds board specific workarounds to each of the device >>>>> drivers. It might be easier to have that managed in a central place. >>>> >>>> Right, I considered that, and I'm actually doing pretty much that for >>>> a somewhat similar ACPI case, see: >>>> >>>> drivers/platform/x86/intel_cht_int33fe.c >>>> >>>> But there things were more complicated and we also needed to attach >>>> device-properties, while at the same time we were also somewhat lucky, >>>> because there are 4 I2cSerialBusV2 resources in the single ACPI fwnode >>>> and we only care about 2-4, so we can have an i2c-driver in >>>> platform/drivers/x86 bind to the 1st resource and then have it >>>> instantiate i2c clients for I2cSerialBusV2 resources 2-4. >>>> >>>> The problem with the BSG1160 case is that we want to also have an >>>> iio driver bind to the first i2c-client and that will not work >>>> if an i2c-driver in platform/drivers/x86 binds to the first >>>> i2c-client and the i2c-subsys will rightfully not let us create another >>>> i2c-client at the same address. >>>> >>>> About the "board specific workarounds for each of the drivers", I could >>>> check if they are all checking an id register and if so if I could just >>>> let all 3 of them try to bind without issues. This will likely still >>>> require a change to log the id not matching add a less severe log-level. >>> >>> p.s. >>> >>> Also there seems to be a pattern here where this is happening more >>> often, e.g. see also: >>> >>> https://fedorapeople.org/~jwrdegoede/lenovo-yoga-11e-dstd.dsl >>> Search for BOSC0200 to find a single Device() blurb describing >>> 2 bma250 accelerometers at 2 different addresses. >>> >>> And having to write a whole new driver each time this happens is >>> going to become tedious pretty quick and also seems undesirable. >>> >>> Just adding a HID to an id-table OTOH for each case seems like a >>> better (less sucking) solution. >> >> I'd use the same argument to argue for the opposite. The fact that is is a >> common occurrence means it should not be handled in the device driver, >> because it means you'll end up having to add quirks for each and every >> vendor binding. >> >> E.g. if you look at the example you provided there is also a mounting matrix >> and calibration data for each of the two sensors. You need a way to map >> those to the individual devices. >> >>> >>> So I think we should not focus too much on the BSG1160 example >>> and more try to come up with a generic solution for this as >>> Andy has done. >> >> I agree that a generic solution is the right approach, but I do not think >> that adding lots of individual quirks to device drivers is a generic >> solution. >> >> Maybe we can teach the I2C framework about these hub nodes, so that the >> device for the hub itself does not prevent the children from binding to >> their I2C addresses. You are already patching the I2C core anyway. > > Ok, so thinking more about this I think that we indeed need to solve this > differently. Another argument here is to also not pollute the i2c core > with a whole bunch of extra code, just to handle these corner cases. > > So my idea is to have an i2c-driver under platform/x86 which deals with > these special cases where we want multiple i2c-clients instantiated > from a single ACPI fwnode. > > The idea is to have a bool no_address_busy_check in i2c_board_info, > with a big fat comment that it is special and should be avoided, > which disables the i2c_check_addr_busy() check in i2c_new_device(). Ideally we'd be able to register the hub as an address-less device and then have each of the sensors bind to their respective I2C addresses while still making sure that there are no address duplicates. Maybe is possible to re-use part of the I2C MUX infrastructure and have the hub register itself as some kind of MUX device and the sensors as children to the hub. This way the sensors would still be grouped in the device hierarchy. -- 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
