On Monday, June 06, 2016 11:03:26 PM Crestez Dan Leonard wrote: > Linux supports instantiating devices using devicetree ids from ACPI by setting > the id to PRP0001 and adding the devicetree compatible string in _DSD > properties. This is described in Documentation/acpi/enumeration.txt. > > I've tried to use this feature using custom ACPI tables and one issue I > encountered is that a lot of i2c device drivers are written for DT only and > expect a valid i2c_device_id *id parameter to their probe function but this is > always NULL for the PRP0001 case. Others call of_match_device in order to > determine their exact model number and that will also fail. > > Drivers normally do this in order to differentiate between minor model numbers > supported by the same driver, for example hmc5883 versus hmc5983. > > For ACPI it is common to add calls to acpi_match_device in order to do such > differentiation. It might make sense to call some form of acpi_of_match_device > except no such function is currently exported. I think it makes a lot of sense > to refactor the current acpi_of_match_device to return the of_device_id and > export it. > > This is in PATCH 1. After exposing this function it could be called from each > driver that needs to support multiple models through PRP0001. I guess the > alternative to exposing acpi_of_match_device would be for driver code to poke > at acpi_device->data.of_compatible? > > Going further it might make sense to attempt to fetch the i2c_device_id when > instantiating through PRP0001. This already happens automatically for > devicetree and it makes a lot of sense it would work through ACPI with DT ids. > Patch 2 hacks an additional search in i2c register code. This makes some > drivers "just work" without manually handling the "ACPI with DT ids" case. > > For P1 it might make sense to change the parameters around so that > acpi_of_match_device will have the same signature as of_match_device. > > The purpose of these changes would be to make more drivers easier to > instantiate through ACPI firmware. It's possible that I misunderstood and this > problem already has a different solution. > > Crestez Dan Leonard (2): > acpi: Expose acpi_of_match_device > i2c: Pass i2c_device_id to probe func when using DT ids through ACPI It would be good to CC the actual patches to the same set of addresses as this message. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
