Re: [PATCH v7 4/5] iio: trigger: Introduce IIO hrtimer based trigger

[Vladimir Barinov]

Hello Daniel,

I've verified that your hrtimer trigger works.

I have minor suggestions.

Will not it be useful to have ability to stop/start hrtimer polling
not only during attach/detach trigger.

f.e. writing 0 to sampling_frequency will hrtimer_cancel
and writing any valid frequency will hrtimer_start.

Regards,
Vladimir

On 11.08.2015 01:42, Daniel Baluta wrote:
> This patch registers a new IIO software trigger interrupt source
> based on high resolution timers.
>
> Notice that if configfs is enabled we create sampling_frequency
> attribute allowing users to change hrtimer period (1/sampling_frequency).
>
> The IIO hrtimer trigger has a long history, this patch is based on
> an older version from Marten and Lars-Peter.
>
> Signed-off-by: Marten Svanfeldt <marten@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> ---
>   drivers/iio/trigger/Kconfig            |  10 ++
>   drivers/iio/trigger/Makefile           |   2 +
>   drivers/iio/trigger/iio-trig-hrtimer.c | 193 +++++++++++++++++++++++++++++++++
>   3 files changed, 205 insertions(+)
>   create mode 100644 drivers/iio/trigger/iio-trig-hrtimer.c
>
> diff --git a/drivers/iio/trigger/Kconfig b/drivers/iio/trigger/Kconfig
> index 7999612..4505281 100644
> --- a/drivers/iio/trigger/Kconfig
> +++ b/drivers/iio/trigger/Kconfig
> @@ -5,6 +5,16 @@
>   
>   menu "Triggers - standalone"
>   
> +config IIO_HRTIMER_TRIGGER
> +	tristate "High resolution timer trigger"
> +	select IIO_SW_TRIGGER
> +	help
> +	  Provides a frequency based IIO trigger using high resolution
> +	  timers as interrupt source.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called iio-trig-hrtimer.
> +
>   config IIO_INTERRUPT_TRIGGER
>   	tristate "Generic interrupt trigger"
>   	help
> diff --git a/drivers/iio/trigger/Makefile b/drivers/iio/trigger/Makefile
> index 0694dae..fe06eb5 100644
> --- a/drivers/iio/trigger/Makefile
> +++ b/drivers/iio/trigger/Makefile
> @@ -3,5 +3,7 @@
>   #
>   
>   # When adding new entries keep the list in alphabetical order
> +
> +obj-$(CONFIG_IIO_HRTIMER_TRIGGER) += iio-trig-hrtimer.o
>   obj-$(CONFIG_IIO_INTERRUPT_TRIGGER) += iio-trig-interrupt.o
>   obj-$(CONFIG_IIO_SYSFS_TRIGGER) += iio-trig-sysfs.o
> diff --git a/drivers/iio/trigger/iio-trig-hrtimer.c b/drivers/iio/trigger/iio-trig-hrtimer.c
> new file mode 100644
> index 0000000..4631c7a
> --- /dev/null
> +++ b/drivers/iio/trigger/iio-trig-hrtimer.c
> @@ -0,0 +1,193 @@
> +/**
> + * The industrial I/O periodic hrtimer trigger driver
> + *
> + * Copyright (C) Intuitive Aerial AB
> + * Written by Marten Svanfeldt, marten@xxxxxxxxxxxxxxxxxxx
> + * Copyright (C) 2012, Analog Device Inc.
> + *	Author: Lars-Peter Clausen <lars@xxxxxxxxxx>
> + * Copyright (C) 2015, Intel Corporation
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + */
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/hrtimer.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/sw_trigger.h>
> +
> +/* default sampling frequency - 100Hz */
> +#define HRTIMER_DEFAULT_SAMPLING_FREQUENCY 100
> +
> +struct iio_hrtimer_info {
> +	struct iio_sw_trigger swt;
> +	struct hrtimer timer;
> +	unsigned long sampling_frequency;
> +	ktime_t period;
> +};
> +
> +static struct config_item_type iio_hrtimer_type = {
> +	.ct_owner = THIS_MODULE,
> +};
> +
> +static
> +ssize_t iio_hrtimer_show_sampling_frequency(struct device *dev,
> +					    struct device_attribute *attr,
> +					    char *buf)
> +{
> +	struct iio_trigger *trig = to_iio_trigger(dev);
> +	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);
> +
> +	return snprintf(buf, PAGE_SIZE, "%lu\n", info->sampling_frequency);
> +}
> +
> +static
> +ssize_t iio_hrtimer_store_sampling_frequency(struct device *dev,
> +					     struct device_attribute *attr,
> +					     const char *buf, size_t len)
> +{
> +	struct iio_trigger *trig = to_iio_trigger(dev);
> +	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);
> +	unsigned long val;
> +	int ret;
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (!val || val > NSEC_PER_SEC)
> +		return -EINVAL;
> +
> +	info->sampling_frequency = val;
> +	info->period = ktime_set(0, NSEC_PER_SEC / val);
> +
> +	return len;
> +}
> +
> +static DEVICE_ATTR(sampling_frequency, S_IRUGO | S_IWUSR,
> +		   iio_hrtimer_show_sampling_frequency,
> +		   iio_hrtimer_store_sampling_frequency);
> +
> +static struct attribute *iio_hrtimer_attrs[] = {
> +	&dev_attr_sampling_frequency.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group iio_hrtimer_attr_group = {
> +	.attrs = iio_hrtimer_attrs,
> +};
> +
> +static const struct attribute_group *iio_hrtimer_attr_groups[] = {
> +	&iio_hrtimer_attr_group,
> +	NULL
> +};
> +
> +static enum hrtimer_restart iio_hrtimer_trig_handler(struct hrtimer *timer)
> +{
> +	struct iio_hrtimer_info *info;
> +
> +	info = container_of(timer, struct iio_hrtimer_info, timer);
> +
> +	hrtimer_forward_now(timer, info->period);
> +	iio_trigger_poll(info->swt.trigger);
> +
> +	return HRTIMER_RESTART;
> +}
> +
> +static int iio_trig_hrtimer_set_state(struct iio_trigger *trig, bool state)
> +{
> +	struct iio_hrtimer_info *trig_info;
> +
> +	trig_info = iio_trigger_get_drvdata(trig);
> +
> +	if (state)
> +		hrtimer_start(&trig_info->timer, trig_info->period,
> +			      HRTIMER_MODE_REL);
> +	else
> +		hrtimer_cancel(&trig_info->timer);
> +
> +	return 0;
> +}
> +
> +static const struct iio_trigger_ops iio_hrtimer_trigger_ops = {
> +	.owner = THIS_MODULE,
> +	.set_trigger_state = iio_trig_hrtimer_set_state,
> +};
> +
> +static struct iio_sw_trigger *iio_trig_hrtimer_probe(const char *name)
> +{
> +	struct iio_hrtimer_info *trig_info;
> +	int ret;
> +
> +	trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
> +	if (!trig_info)
> +		return ERR_PTR(-ENOMEM);
> +
> +	trig_info->swt.trigger = iio_trigger_alloc("%s", name);
> +	if (!trig_info->swt.trigger) {
> +		ret = -ENOMEM;
> +		goto err_free_trig_info;
> +	}
> +
> +	iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
> +	trig_info->swt.trigger->ops = &iio_hrtimer_trigger_ops;
> +	trig_info->swt.trigger->dev.groups = iio_hrtimer_attr_groups;
> +
> +	hrtimer_init(&trig_info->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +	trig_info->timer.function = iio_hrtimer_trig_handler;
> +
> +	trig_info->sampling_frequency = HRTIMER_DEFAULT_SAMPLING_FREQUENCY;
> +	trig_info->period = ktime_set(0, NSEC_PER_SEC /
> +				      trig_info->sampling_frequency);
> +
> +	ret = iio_trigger_register(trig_info->swt.trigger);
> +	if (ret)
> +		goto err_free_trigger;
> +
> +	iio_swt_group_init_type_name(&trig_info->swt, name, &iio_hrtimer_type);
> +	return &trig_info->swt;
> +err_free_trigger:
> +	iio_trigger_free(trig_info->swt.trigger);
> +err_free_trig_info:
> +	kfree(trig_info);
> +
> +	return ERR_PTR(ret);
> +}
> +
> +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);
> +
> +	iio_trigger_unregister(swt->trigger);
> +
> +	/* cancel the timer after unreg to make sure no one rearms it */
> +	hrtimer_cancel(&trig_info->timer);
> +	iio_trigger_free(swt->trigger);
> +	kfree(trig_info);
> +
> +	return 0;
> +}
> +
> +const struct iio_sw_trigger_ops iio_trig_hrtimer_ops = {
> +	.probe		= iio_trig_hrtimer_probe,
> +	.remove		= iio_trig_hrtimer_remove,
> +};
> +
> +struct iio_sw_trigger_type iio_trig_hrtimer = {
> +	.name = "hrtimer",
> +	.owner = THIS_MODULE,
> +	.ops = &iio_trig_hrtimer_ops,
> +};
> +
> +module_iio_sw_trigger_driver(iio_trig_hrtimer);
> +
> +MODULE_AUTHOR("Marten Svanfeldt <marten@xxxxxxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Periodic hrtimer trigger for the IIO subsystem");
> +MODULE_LICENSE("GPL v2");

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