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. v2 fixes the code to actually work correctly. Hopefully the patches will also be sent to the correct addresses this time. Crestez Dan Leonard (2): acpi: Expose acpi_of_match_device i2c: Pass i2c_device_id to probe func when using DT ids through ACPI drivers/acpi/bus.c | 13 +++++++------ drivers/i2c/i2c-core.c | 30 ++++++++++++++++++++++++++---- include/linux/acpi.h | 8 ++++++++ 3 files changed, 41 insertions(+), 10 deletions(-) -- 2.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
