On Tue, Oct 13, 2015 at 08:54:12AM +0000, Tirdea, Irina wrote: > > > I did not use devm_gpiod_get_optional() in order to ignore more errors > > > than -ENOENT. This is needed because the ACPI gpio core will fall back > > > to indexed gpios if named gpios are not found. In the common case of > > > having 2 indexed gpio pins declared in the ACPI table, the first > > > devm_gpiod_get() will successfully get indexed gpio pin 0 and the > > > second devm_gpiod_get() will try to get the same gpio pin 0 and return > > > -EBUSY. Considering this, I thought it is better to just ignore all errors in > > > order not to break any platforms currently using this driver. > > > > This seems like issue with ACPI gpio lookup implementation. If I am > > requesting named gpio and it is not present then I definitely do not > > need to be returned some random gpio. Doing so breaks all other drivers > > that use several names to retrieve GPIOs. We basically can't trust GPIO > > API on ACPI systems. > > > > I'm not sure there is a way to avoid fall back to indexed gpios when requesting > named gpios. > Adding Mika to this thread as he might help answer this. Before ACPI 5.1 _DSD device properties were introduced all we had was an array of GPIOs returned by _CRS ACPI method. Ordering of those GPIOs could change from one vendor to another :-( We can (and do) use acpi_dev_add_driver_gpios() to pass correct mappings where _DSD is not present based on the device ACPI ID for instance. Not all drivers do that, though. I would like to get rid of the fallback completely at some point. We have had already problems with the API because then some ACPI only drivers did this: reset_gpio = gpiod_get_index(dev, NULL, 0); power_gpio = gpiod_get_index(dev, NULL, 1); which might not do what is expected on DT systems. That's why acpi_dev_add_driver_gpios() was added in the first place IIRC. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
