Re: [PATCH v2 1/2] ARM: davinci: Allocate extra interrupts

From: David Lechner
Date: Fri Jan 20 2017 - 13:17:12 EST


On 01/20/2017 05:50 AM, Sekhar Nori wrote:
On Wednesday 18 January 2017 10:27 PM, David Lechner wrote:
On 01/18/2017 03:50 AM, Sekhar Nori wrote:
On Saturday 14 January 2017 01:30 AM, David Lechner wrote:
This allocates extra interrupts for mach-davinci. These extra interrupts
are need for things like IIO triggers.

I am not really familiar with IIO triggers. Can you give some more
detail on what fails without this patch?

A trigger is used to initiate the reading of an iio device. For example,
there is a mechanism for a sysfs trigger. When you write 1 to the sysfs
attribute, it triggers an interrupt that is handled by the iio device.

Since these triggers use interrupts, you need to allocate spare
interrupts in order to set up the trigger. Otherwise, setting up the
trigger will fail with an error code (I forgot which one exactly)
because all of the allocated irqs have already been assigned to hardware
irqs and are not available.

Here is where the iio subsytem actually allocates the irq:
http://lxr.free-electrons.com/source/drivers/iio/industrialio-trigger.c#L525

Alright, I will take a look. Do note that this may not get included in
the first batch of v4.11 changes I queue. But I promise to come back to
it soon afterwards.


It is not critical at this point, so it is fine to wait a bit.