linux-kernel - Re: [PATCH v1 0/2] iio: Add parent

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Date:   Sat, 11 Feb 2017 10:23:27 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v1 0/2] iio: Add parent_trigger attribute to triggers

On 06/02/17 14:43, Benjamin Gaignard wrote:
> 2017-02-06 15:26 GMT+01:00 Lars-Peter Clausen <lars@...afoo.de>:
>> On 02/06/2017 03:21 PM, Benjamin Gaignard wrote:
>>> Thoses patches add parent_trigger attribute to IIO triggers.
>>> The goal is to allow triggers to use triggers like is this done for iio
>>> devices.
>>> With this patch it will be possible to chain triggers, for example
>>> stm32 triggers could be used as clock of an other triggers:
>>> echo "tim1_trgo" > trigger0/parent_trigger.
>>
>> Can you explain how this is different to assigning the parent_trigger
>> directly to the device?
>>
> 
> It is the same but done on trigger structure without need to have an iio device.
> 
> While writing stm32 trigger driver Jonathan explain me that I can't use an iio
> device without channel to chain my hardware blocks.
> Since my hardware allows to chain triggers, Jonathan suggest to create this
> parent_trigger attribute to ab able to link the triggers.
> 
I think Lars was looking for the more general explanation.  How does
one trigger drive another one?  What does that mean?