On Fri, Aug 08, 2014 at 02:36:02PM +0200, Linus Walleij wrote:
On Thu, Jul 24, 2014 at 5:51 PM, Tomasz Nowicki tomasz.nowicki@linaro.org wrote:
GPIO signaled events is quite new thing in Linux kernel. AFAIK, there are not many board which can take advantage of it. However, GPIO events are very useful feature during work on ACPI subsystems.
Overall this seems like a pretty nice debug feature.
This commit emulates GPIO h/w behaviour and consists on read/write operation to debugfs file. GPIO device instance is still required in DSDT table along with _AEI resources and event methods.
Reading from file provides pin to GPIO device map e.g. : $ cat /sys/kernel/debug/acpi/gpio_event GPIO device name: /__SB.GPI0 Available GPIO pin map: /__SB.GPI0 <-> pin 0x100
Based on that, user can trigger method corresponding to device pin number: $ echo "/__SB.GPI0 0x100" > /sys/kernel/debug/acpi/gpio_event
I need input from Rafael and Mika as to whether this is a good interface.
Maybe it would make sense to move this into drivers/gpio/gpiolib-acpi.c and hide it behind some Kconfig entry?
Since you already need to have DSDT/SSDT table for this to provide the GPIO device, _AEI and the event methods, I would rather make it so that acpi_gpiochip_request_interrupt() will add debugfs entry for each GPIO it finds in _AEI, like:
/sys/kernel/debug/acpi/events/<GPIO DEVICE>/n
And you could trigger it by writing '1' or something like that to that file.