On 09/22/2013 08:40 AM, Javier Martinez Canillas wrote:

To use a GPIO pin as an interrupt line, two previous configurations
have to be made:

a) Map the GPIO pin as an interrupt line into the Linux irq space
b) Enable the GPIO bank and configure the GPIO direction as input

Most GPIO/IRQ chip drivers just create a mapping for every single
GPIO pin with irq_create_mapping() on .probe so users usually can
assume a) and only have to do b) by using the following sequence:

gpio_request(gpio, "foo IRQ");
gpio_direction_input(gpio);

and then request a IRQ with:

irq = gpio_to_irq(gpio);
request_irq(irq, ...);

Some drivers know that their IRQ line is being driven by a GPIO
and use a similar sequence as the described above but others are
not aware or don't care wether their IRQ is a real line from an
interrupt controller or a GPIO pin acting as an IRQ.
...

I think that explanation is a bit like retro-actively implying that
drivers /should/ be aware of whether their IRQ is a GPIO or not, and
should be acting differently. However, they should not.

I would much rather see a simpler patch description along the lines of:

The OMAP GPIO controller HW requires that a pin be configured in GPIO
mode in order to operate as an interrupt input. Since drivers should not
be aware of whether an interrupt pin is also a GPIO or not, the HW
should be fully configured/enabled as an IRQ if a driver solely uses IRQ
APIs such as request_irq, and never calls any GPIO-related APIs. As
such, add the missing HW setup to the OMAP GPIO controller's irq_chip
driver.

The code change looks like it does what I would expect though.
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