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

[Daniel Baluta]

On Wed, May 6, 2015 at 8:16 PM, Jonathan Cameron <jic23@xxxxxxxxxx> 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@xxxxxxxxxx> 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.
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