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

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Date:	Tue, 05 May 2015 14:51:05 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Lars-Peter Clausen <lars@...afoo.de>,
	Daniel Baluta <daniel.baluta@...el.com>
CC:	jlbec@...lplan.org, knaack.h@....de, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, octavian.purdila@...el.com,
	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 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.
>
>[...]
>> +#endif /* CONFIGFS_FS */
>> +
>[...]
>> +static struct iio_sw_trigger *iio_trig_hrtimer_probe(const char
>*name)
>> +{
>[...]
>> +#ifdef CONFIG_CONFIGFS_FS
>> +	config_group_init_type_name(&trig_info->swt.group, name,
>> +				    &iio_hrtimer_type);
>> +#endif
>
>This should probably have a helper function in the sw trigger core,
>that 
>gets stubbed out when CONFIG_FS is disabled. Otherwise we'll see the
>same 
>#ifdef in every software trigger driver.
>[...]
>> +}
>> +
>> +static int iio_trig_hrtimer_remove(struct iio_sw_trigger *swt)
>> +{
>> +	struct iio_hrtimer_info *trig_info;
>> +
>> +	trig_info = iio_trigger_get_drvdata(swt->trigger);
>> +
>> +	hrtimer_cancel(&trig_info->timer);
>> +
>> +	iio_trigger_unregister(swt->trigger);
>> +	iio_trigger_free(swt->trigger);
>
>There is a bit of a race condition here. hrtimer_cancel() should be
>called 
>between unregister and free, otherwise it might be re-armed before it
>is 
>unregistered.
>
>> +	kfree(trig_info);
>> +
>> +	return 0;
>> +}
>> +
>> +struct iio_sw_trigger_ops iio_trig_hrtimer_ops = {
>
>const
>
>> +	.probe		= iio_trig_hrtimer_probe,
>> +	.remove		= iio_trig_hrtimer_remove,
>> +};
>[...]
>
>--
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