linux-kernel - Re: [PATCH v5 3/4] iio: trigger: Introduce IIO hrtimer based trigger

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Message-ID: <554B2E22.10807@kernel.org>
Date:	Thu, 07 May 2015 10:19:30 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Daniel Baluta <daniel.baluta@...el.com>
CC:	Lars-Peter Clausen <lars@...afoo.de>,
	Joel Becker <jlbec@...lplan.org>,
	Hartmut Knaack <knaack.h@....de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"octavian.purdila@...el.com" <octavian.purdila@...el.com>,
	Paul Bolle <pebolle@...cali.nl>, patrick.porlan@...el.com,
	adriana.reus@...el.com, constantin.musca@...el.com,
	marten@...uitiveaerial.com
Subject: Re: [PATCH v5 3/4] iio: trigger: Introduce IIO hrtimer based trigger

On 06/05/15 18:37, Daniel Baluta wrote:
> On Wed, May 6, 2015 at 8:16 PM, Jonathan Cameron <jic23@...nel.org> wrote:
>> On 06/05/15 17:25, Daniel Baluta wrote:
>>>
>>>
>>> On 05/05/2015 04:51 PM, Jonathan Cameron wrote:
>>>>
>>>>
>>>> On 4 May 2015 20:54:08 GMT+01:00, Lars-Peter Clausen <lars@...afoo.de> wrote:
>>>>> On 05/04/2015 12:50 PM, Daniel Baluta wrote:
>>>>> [...]
>>>>>> +IIO_HRTIMER_INFO_ATTR(sampling_frequency, S_IRUGO | S_IWUSR,
>>>>>> +              iio_hrtimer_info_show_sampling_frequency,
>>>>>> +              iio_hrtimer_info_store_sampling_frequency);
>>>>>
>>>>> I wonder if the sampling frequency should be configurable the regular
>>>>> IIO
>>>>> API, just like any other IIO device. But things like min/max sampling
>>>>> frequency should be configured in configfs.
>>>> Would have to be in the trigger dir rather than device... Makes sense to put it there.
>>>> Limits on it here seem like a sensible idea.
>>>
>>> But then each trigger will have sampling_frequency right? This is not what we want.
>> I'm confused now.  Why not?  Each hrtimer trigger created in configfs should have
>> it's own sampling frequency should it not?
> 
> I was referring to triggers in general, not just hrtimer triggers.
> 
> But I see now that we can set trig->dev.groups to point to our
> specific attributes. This
> should work.
> 
> Anyhow, I'm not convinced that sampling_frequency should be configured
> from sysfs.
> We create the trigger from configfs:
> 
> $ mkdir /config/triggers/hrtimer-instance0
> 
> Then, likely we have to do something like this:
> 
> $ echo 100 > /sys/bus/iio/trigger7/sampling_frequency
> 
> How is the user application going to know which is the exact directory
> for hrtimer-instance0 ?
> 
> Daniel.
> 
Find it by name like we normally do?

J

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