From: David Lechner <david@lechnology.com>
To: Sekhar Nori <nsekhar@ti.com>, linux-arm-kernel@lists.infradead.org
Cc: Kevin Hilman <khilman@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] ARM: davinci: Allocate extra interrupts
Date: Wed, 18 Jan 2017 10:57:31 -0600 [thread overview]
Message-ID: <25c0bc60-bb99-9aa5-db56-6299d82db9c1@lechnology.com> (raw)
In-Reply-To: <95440160-8346-fef8-27d2-fb17c0da38f6@ti.com>
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
next prev parent reply other threads:[~2017-01-18 16:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 20:00 [PATCH v2 0/2] ARM: davinci_all_defconfig: enable iio David Lechner
2017-01-13 20:00 ` [PATCH v2 1/2] ARM: davinci: Allocate extra interrupts David Lechner
2017-01-18 9:50 ` Sekhar Nori
2017-01-18 16:57 ` David Lechner [this message]
2017-01-20 11:50 ` Sekhar Nori
2017-01-20 18:17 ` David Lechner
2017-02-02 15:06 ` Sekhar Nori
2017-02-07 19:42 ` David Lechner
2017-01-13 20:00 ` [PATCH v2 2/2] ARM: davinci_all_defconfig: enable iio David Lechner
2017-01-20 11:51 ` Sekhar Nori
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