iio:trigger: Introduce iio_tigger_{set,get}_drvdata

Introduce iio_tigger_{set,get}_drvdata which allows to attach driver specific
data to a trigger. The functions wrap access to the triggers private_data field
and all current users are updated to use iio_tigger_{set,get}_drvdata instead of
directly accessing the private_data field. This is the first step towards
removing the private_data field from the iio_trigger struct.

The following coccinelle script has been used to update the drivers:
<smpl>
@@
struct iio_trigger *trigger;
expression priv;
@@
-trigger->private_data = priv
+iio_trigger_set_drv_data(trigger, priv)

@@
struct iio_trigger *trigger;
@@
-trigger->private_data
+iio_trigger_get_drv_data(trigger)
</smpl>

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/accel/st_accel_buffer.c b/drivers/iio/accel/st_accel_buffer.c
index 6bd82c7f769c51a7b45bbb81bb5d62ddf10daf31..d9b350756f90f11d1bc77cd88362fe45639d295e 100644 (file)
--- a/drivers/iio/accel/st_accel_buffer.c
+++ b/drivers/iio/accel/st_accel_buffer.c
@@ -25,7 +25,7 @@
 
 int st_accel_trig_set_state(struct iio_trigger *trig, bool state)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
 
        return st_sensors_set_dataready_irq(indio_dev, state);
 }

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index afe6d78c8ff0f6cf4dcb54727e2999749010bdba..f0d6335ae08760d418f56ced0eaec227772fa1ce 100644 (file)
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -470,7 +470,7 @@ static int ad_sd_probe_trigger(struct iio_dev *indio_dev)
                disable_irq_nosync(sigma_delta->spi->irq);
        }
        sigma_delta->trig->dev.parent = &sigma_delta->spi->dev;
-       sigma_delta->trig->private_data = sigma_delta;
+       iio_trigger_set_drvdata(sigma_delta->trig, sigma_delta);
 
        ret = iio_trigger_register(sigma_delta->trig);
        if (ret)

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 92eb6a5b9e72b1a34915628f934715a0e1307646..6fc43c15f02878a295c80d9aab6fbcbbe00f98c1 100644 (file)
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -188,7 +188,7 @@ static u8 at91_adc_get_trigger_value_by_name(struct iio_dev *idev,
 
 static int at91_adc_configure_trigger(struct iio_trigger *trig, bool state)
 {
-       struct iio_dev *idev = trig->private_data;
+       struct iio_dev *idev = iio_trigger_get_drvdata(trig);
        struct at91_adc_state *st = iio_priv(idev);
        struct iio_buffer *buffer = idev->buffer;
        struct at91_adc_reg_desc *reg = st->registers;
@@ -254,7 +254,7 @@ static struct iio_trigger *at91_adc_allocate_trigger(struct iio_dev *idev,
                return NULL;
 
        trig->dev.parent = idev->dev.parent;
-       trig->private_data = idev;
+       iio_trigger_set_drvdata(trig, idev);
        trig->ops = &at91_adc_trigger_ops;
 
        ret = iio_trigger_register(trig);

diff --git a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
index 7a525a91105d38a7570c1caddf85e41bdaf9553d..87419c41b991da24d8d284d33502c81f72c1c377 100644 (file)
--- a/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
+++ b/drivers/iio/common/hid-sensors/hid-sensor-trigger.c
@@ -31,7 +31,7 @@
 static int hid_sensor_data_rdy_trigger_set_state(struct iio_trigger *trig,
                                                bool state)
 {
-       struct hid_sensor_common *st = trig->private_data;
+       struct hid_sensor_common *st = iio_trigger_get_drvdata(trig);
        int state_val;
 
        state_val = state ? 1 : 0;
@@ -76,7 +76,7 @@ int hid_sensor_setup_trigger(struct iio_dev *indio_dev, const char *name,
        }
 
        trig->dev.parent = indio_dev->dev.parent;
-       trig->private_data = attrb;
+       iio_trigger_set_drvdata(trig, attrb);
        trig->ops = &hid_sensor_trigger_ops;
        ret = iio_trigger_register(trig);
 

diff --git a/drivers/iio/common/st_sensors/st_sensors_trigger.c b/drivers/iio/common/st_sensors/st_sensors_trigger.c
index 139ed030abb0615f2c316990e6b3aa92b6c092c2..8fc3a97eb266e6302367653248017c3b6078a021 100644 (file)
--- a/drivers/iio/common/st_sensors/st_sensors_trigger.c
+++ b/drivers/iio/common/st_sensors/st_sensors_trigger.c
@@ -40,7 +40,7 @@ int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
        if (err)
                goto request_irq_error;
 
-       sdata->trig->private_data = indio_dev;
+       iio_trigger_set_drvdata(sdata->trig, indio_dev);
        sdata->trig->ops = trigger_ops;
        sdata->trig->dev.parent = sdata->dev;
 

diff --git a/drivers/iio/gyro/itg3200_buffer.c b/drivers/iio/gyro/itg3200_buffer.c
index f667d2c8c00f0c417a04caab2c1a694e016e96a1..6c43af9bb0a4474097f2def7ec15d973a7238b47 100644 (file)
--- a/drivers/iio/gyro/itg3200_buffer.c
+++ b/drivers/iio/gyro/itg3200_buffer.c
@@ -81,7 +81,7 @@ void itg3200_buffer_unconfigure(struct iio_dev *indio_dev)
 static int itg3200_data_rdy_trigger_set_state(struct iio_trigger *trig,
                bool state)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        int ret;
        u8 msc;
 
@@ -129,7 +129,7 @@ int itg3200_probe_trigger(struct iio_dev *indio_dev)
 
        st->trig->dev.parent = &st->i2c->dev;
        st->trig->ops = &itg3200_trigger_ops;
-       st->trig->private_data = indio_dev;
+       iio_trigger_set_drvdata(st->trig, indio_dev);
        ret = iio_trigger_register(st->trig);
        if (ret)
                goto error_free_irq;

diff --git a/drivers/iio/gyro/st_gyro_buffer.c b/drivers/iio/gyro/st_gyro_buffer.c
index da4d122ec7dc1a4efb4aec0d4fe1e1eb6a33a1a1..69017c7ec302a785ffd86afca90ff3b2ae1e9d3e 100644 (file)
--- a/drivers/iio/gyro/st_gyro_buffer.c
+++ b/drivers/iio/gyro/st_gyro_buffer.c
@@ -25,7 +25,7 @@
 
 int st_gyro_trig_set_state(struct iio_trigger *trig, bool state)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
 
        return st_sensors_set_dataready_irq(indio_dev, state);
 }

diff --git a/drivers/iio/imu/adis_trigger.c b/drivers/iio/imu/adis_trigger.c
index 5a24c9cac3436ae3d833cac2c58b6913f4588dcc..e0017c22bb9c6ce3b4f4f9c753a8ce1364621b19 100644 (file)
--- a/drivers/iio/imu/adis_trigger.c
+++ b/drivers/iio/imu/adis_trigger.c
@@ -19,7 +19,7 @@
 static int adis_data_rdy_trigger_set_state(struct iio_trigger *trig,
                                                bool state)
 {
-       struct adis *adis = trig->private_data;
+       struct adis *adis = iio_trigger_get_drvdata(trig);
 
        return adis_enable_irq(adis, state);
 }
@@ -57,7 +57,7 @@ int adis_probe_trigger(struct adis *adis, struct iio_dev *indio_dev)
 
        adis->trig->dev.parent = &adis->spi->dev;
        adis->trig->ops = &adis_trigger_ops;
-       adis->trig->private_data = adis;
+       iio_trigger_set_drvdata(adis->trig, adis);
        ret = iio_trigger_register(adis->trig);
 
        indio_dev->trig = adis->trig;

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
index e1d0869e0ad174545bccaec73c13eb685e977fec..03b9372c1212a99c5a6a2452cc081f7395a259ca 100644 (file)
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_trigger.c
@@ -103,7 +103,7 @@ static int inv_mpu6050_set_enable(struct iio_dev *indio_dev, bool enable)
 static int inv_mpu_data_rdy_trigger_set_state(struct iio_trigger *trig,
                                                bool state)
 {
-       return inv_mpu6050_set_enable(trig->private_data, state);
+       return inv_mpu6050_set_enable(iio_trigger_get_drvdata(trig), state);
 }
 
 static const struct iio_trigger_ops inv_mpu_trigger_ops = {
@@ -130,8 +130,8 @@ int inv_mpu6050_probe_trigger(struct iio_dev *indio_dev)
        if (ret)
                goto error_free_trig;
        st->trig->dev.parent = &st->client->dev;
-       st->trig->private_data = indio_dev;
        st->trig->ops = &inv_mpu_trigger_ops;
+       iio_trigger_set_drvdata(st->trig, indio_dev);
        ret = iio_trigger_register(st->trig);
        if (ret)
                goto error_free_irq;

diff --git a/drivers/staging/iio/accel/lis3l02dq_ring.c b/drivers/staging/iio/accel/lis3l02dq_ring.c
index e676403ea3ea6cbc3dff62d7a720d6786314e474..5b8f0f6c99385d409ba471acfe902a041518da38 100644 (file)
--- a/drivers/staging/iio/accel/lis3l02dq_ring.c
+++ b/drivers/staging/iio/accel/lis3l02dq_ring.c
@@ -228,7 +228,7 @@ error_ret:
 static int lis3l02dq_data_rdy_trigger_set_state(struct iio_trigger *trig,
                                                bool state)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        int ret = 0;
        u8 t;
 
@@ -252,7 +252,7 @@ static int lis3l02dq_data_rdy_trigger_set_state(struct iio_trigger *trig,
  */
 static int lis3l02dq_trig_try_reen(struct iio_trigger *trig)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct lis3l02dq_state *st = iio_priv(indio_dev);
        int i;
 
@@ -290,7 +290,7 @@ int lis3l02dq_probe_trigger(struct iio_dev *indio_dev)
 
        st->trig->dev.parent = &st->us->dev;
        st->trig->ops = &lis3l02dq_trigger_ops;
-       st->trig->private_data = indio_dev;
+       iio_trigger_set_drvdata(st->trig, indio_dev);
        ret = iio_trigger_register(st->trig);
        if (ret)
                goto error_free_trig;

diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 25a4359a92dbe0e418dc98156ba69a6ccc0e8279..eab975d11bb281f75264291e40acb5cec325b030 100644 (file)
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -646,7 +646,7 @@ static irqreturn_t mxs_lradc_trigger_handler(int irq, void *p)
 
 static int mxs_lradc_configure_trigger(struct iio_trigger *trig, bool state)
 {
-       struct iio_dev *iio = trig->private_data;
+       struct iio_dev *iio = iio_trigger_get_drvdata(trig);
        struct mxs_lradc *lradc = iio_priv(iio);
        const uint32_t st = state ? STMP_OFFSET_REG_SET : STMP_OFFSET_REG_CLR;
 
@@ -670,7 +670,7 @@ static int mxs_lradc_trigger_init(struct iio_dev *iio)
                return -ENOMEM;
 
        trig->dev.parent = iio->dev.parent;
-       trig->private_data = iio;
+       iio_trigger_set_drvdata(trig, iio);
        trig->ops = &mxs_lradc_trigger_ops;
 
        ret = iio_trigger_register(trig);

diff --git a/drivers/staging/iio/meter/ade7758_trigger.c b/drivers/staging/iio/meter/ade7758_trigger.c
index f9c6a340092b42c97c00b35c3f1958a7ef103772..7a94ddd42f593e7bc1355cd06ebfcb6c400ff014 100644 (file)
--- a/drivers/staging/iio/meter/ade7758_trigger.c
+++ b/drivers/staging/iio/meter/ade7758_trigger.c
@@ -32,7 +32,7 @@ static irqreturn_t ade7758_data_rdy_trig_poll(int irq, void *private)
 static int ade7758_data_rdy_trigger_set_state(struct iio_trigger *trig,
                                                bool state)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
 
        dev_dbg(&indio_dev->dev, "%s (%d)\n", __func__, state);
        return ade7758_set_irq(&indio_dev->dev, state);
@@ -44,7 +44,7 @@ static int ade7758_data_rdy_trigger_set_state(struct iio_trigger *trig,
  **/
 static int ade7758_trig_try_reen(struct iio_trigger *trig)
 {
-       struct iio_dev *indio_dev = trig->private_data;
+       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct ade7758_state *st = iio_priv(indio_dev);
 
        enable_irq(st->us->irq);
@@ -81,7 +81,7 @@ int ade7758_probe_trigger(struct iio_dev *indio_dev)
 
        st->trig->dev.parent = &st->us->dev;
        st->trig->ops = &ade7758_trigger_ops;
-       st->trig->private_data = indio_dev;
+       iio_trigger_set_drvdata(st->trig, indio_dev);
        ret = iio_trigger_register(st->trig);
 
        /* select default trigger */

diff --git a/drivers/staging/iio/trigger/iio-trig-bfin-timer.c b/drivers/staging/iio/trigger/iio-trig-bfin-timer.c
index 42798da575c0bf6c3523a9f028cc739519b7c0a7..38a158b77b1d24f3d55ac12c08ae13b0792b8d20 100644 (file)
--- a/drivers/staging/iio/trigger/iio-trig-bfin-timer.c
+++ b/drivers/staging/iio/trigger/iio-trig-bfin-timer.c
@@ -65,7 +65,7 @@ struct bfin_tmr_state {
 
 static int iio_bfin_tmr_set_state(struct iio_trigger *trig, bool state)
 {
-       struct bfin_tmr_state *st = trig->private_data;
+       struct bfin_tmr_state *st = iio_trigger_get_drvdata(trig);
 
        if (get_gptimer_period(st->t->id) == 0)
                return -EINVAL;
@@ -82,7 +82,7 @@ static ssize_t iio_bfin_tmr_frequency_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
 {
        struct iio_trigger *trig = to_iio_trigger(dev);
-       struct bfin_tmr_state *st = trig->private_data;
+       struct bfin_tmr_state *st = iio_trigger_get_drvdata(trig);
        unsigned long val;
        bool enabled;
        int ret;
@@ -125,7 +125,7 @@ static ssize_t iio_bfin_tmr_frequency_show(struct device *dev,
                                 char *buf)
 {
        struct iio_trigger *trig = to_iio_trigger(dev);
-       struct bfin_tmr_state *st = trig->private_data;
+       struct bfin_tmr_state *st = iio_trigger_get_drvdata(trig);
        unsigned int period = get_gptimer_period(st->t->id);
        unsigned long val;
 
@@ -213,9 +213,9 @@ static int iio_bfin_tmr_trigger_probe(struct platform_device *pdev)
                goto out1;
        }
 
-       st->trig->private_data = st;
        st->trig->ops = &iio_bfin_tmr_trigger_ops;
        st->trig->dev.groups = iio_bfin_tmr_trigger_attr_groups;
+       iio_trigger_set_drvdata(st->trig, st);
        ret = iio_trigger_register(st->trig);
        if (ret)
                goto out2;

diff --git a/drivers/staging/iio/trigger/iio-trig-gpio.c b/drivers/staging/iio/trigger/iio-trig-gpio.c
index fcc4cb048c9a90333f6314e3e687be56338f7672..7c593d18a91079fd9fd557596dc1a274bb136eb8 100644 (file)
--- a/drivers/staging/iio/trigger/iio-trig-gpio.c
+++ b/drivers/staging/iio/trigger/iio-trig-gpio.c
@@ -83,7 +83,7 @@ static int iio_gpio_trigger_probe(struct platform_device *pdev)
                                ret = -ENOMEM;
                                goto error_put_trigger;
                        }
-                       trig->private_data = trig_info;
+                       iio_trigger_set_drvdata(trig, trig_info);
                        trig_info->irq = irq;
                        trig->ops = &iio_gpio_trigger_ops;
                        ret = request_irq(irq, iio_gpio_trigger_poll,
@@ -121,7 +121,7 @@ error_free_completed_registrations:
                                 trig2,
                                 &iio_gpio_trigger_list,
                                 alloc_list) {
-               trig_info = trig->private_data;
+               trig_info = iio_trigger_get_drvdata(trig);
                free_irq(gpio_to_irq(trig_info->irq), trig);
                kfree(trig_info);
                iio_trigger_unregister(trig);
@@ -140,7 +140,7 @@ static int iio_gpio_trigger_remove(struct platform_device *pdev)
                                 trig2,
                                 &iio_gpio_trigger_list,
                                 alloc_list) {
-               trig_info = trig->private_data;
+               trig_info = iio_trigger_get_drvdata(trig);
                iio_trigger_unregister(trig);
                free_irq(trig_info->irq, trig);
                kfree(trig_info);

diff --git a/drivers/staging/iio/trigger/iio-trig-periodic-rtc.c b/drivers/staging/iio/trigger/iio-trig-periodic-rtc.c
index 9102b1ba2530cb6f51616c7f171e7c020189cb43..79695974b1d43dde0a46e1dbf60e00254edd0807 100644 (file)
--- a/drivers/staging/iio/trigger/iio-trig-periodic-rtc.c
+++ b/drivers/staging/iio/trigger/iio-trig-periodic-rtc.c
@@ -30,7 +30,7 @@ struct iio_prtc_trigger_info {
 
 static int iio_trig_periodic_rtc_set_state(struct iio_trigger *trig, bool state)
 {
-       struct iio_prtc_trigger_info *trig_info = trig->private_data;
+       struct iio_prtc_trigger_info *trig_info = iio_trigger_get_drvdata(trig);
        if (trig_info->frequency == 0)
                return -EINVAL;
        printk(KERN_INFO "trigger frequency is %d\n", trig_info->frequency);
@@ -42,7 +42,7 @@ static ssize_t iio_trig_periodic_read_freq(struct device *dev,
                                           char *buf)
 {
        struct iio_trigger *trig = to_iio_trigger(dev);
-       struct iio_prtc_trigger_info *trig_info = trig->private_data;
+       struct iio_prtc_trigger_info *trig_info = iio_trigger_get_drvdata(trig);
        return sprintf(buf, "%u\n", trig_info->frequency);
 }
 
@@ -52,7 +52,7 @@ static ssize_t iio_trig_periodic_write_freq(struct device *dev,
                                            size_t len)
 {
        struct iio_trigger *trig = to_iio_trigger(dev);
-       struct iio_prtc_trigger_info *trig_info = trig->private_data;
+       struct iio_prtc_trigger_info *trig_info = iio_trigger_get_drvdata(trig);
        unsigned long val;
        int ret;
 
@@ -124,7 +124,7 @@ static int iio_trig_periodic_rtc_probe(struct platform_device *dev)
                        ret = -ENOMEM;
                        goto error_put_trigger_and_remove_from_list;
                }
-               trig->private_data = trig_info;
+               iio_trigger_set_drvdata(trig, trig_info);
                trig->ops = &iio_prtc_trigger_ops;
                /* RTC access */
                trig_info->rtc
@@ -158,7 +158,7 @@ error_free_completed_registrations:
                                 trig2,
                                 &iio_prtc_trigger_list,
                                 alloc_list) {
-               trig_info = trig->private_data;
+               trig_info = iio_trigger_get_drvdata(trig);
                rtc_irq_unregister(trig_info->rtc, &trig_info->task);
                rtc_class_close(trig_info->rtc);
                kfree(trig_info);
@@ -176,7 +176,7 @@ static int iio_trig_periodic_rtc_remove(struct platform_device *dev)
                                 trig2,
                                 &iio_prtc_trigger_list,
                                 alloc_list) {
-               trig_info = trig->private_data;
+               trig_info = iio_trigger_get_drvdata(trig);
                rtc_irq_unregister(trig_info->rtc, &trig_info->task);
                rtc_class_close(trig_info->rtc);
                kfree(trig_info);

diff --git a/drivers/staging/iio/trigger/iio-trig-sysfs.c b/drivers/staging/iio/trigger/iio-trig-sysfs.c
index 3bac97224bf4c8683e2f8ac6a180435bf1c0a5b5..b727bde8b7fe09babfc8211be0d61d5c210e2d7c 100644 (file)
--- a/drivers/staging/iio/trigger/iio-trig-sysfs.c
+++ b/drivers/staging/iio/trigger/iio-trig-sysfs.c
@@ -103,7 +103,7 @@ static ssize_t iio_sysfs_trigger_poll(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
 {
        struct iio_trigger *trig = to_iio_trigger(dev);
-       struct iio_sysfs_trig *sysfs_trig = trig->private_data;
+       struct iio_sysfs_trig *sysfs_trig = iio_trigger_get_drvdata(trig);
 
        irq_work_queue(&sysfs_trig->work);
 
@@ -160,7 +160,7 @@ static int iio_sysfs_trigger_probe(int id)
        t->trig->dev.groups = iio_sysfs_trigger_attr_groups;
        t->trig->ops = &iio_sysfs_trigger_ops;
        t->trig->dev.parent = &iio_sysfs_trig_dev;
-       t->trig->private_data = t;
+       iio_trigger_set_drvdata(t->trig, t);
 
        init_irq_work(&t->work, iio_sysfs_trigger_work);
 

diff --git a/include/linux/iio/trigger.h b/include/linux/iio/trigger.h
index c66e0a96f6e8aa9a3d6940e2f563b74e1cae0f8c..b81948aba1d6a2bb3c7f083ac01b7afb71416108 100644 (file)
--- a/include/linux/iio/trigger.h
+++ b/include/linux/iio/trigger.h
@@ -91,6 +91,30 @@ static inline void iio_trigger_get(struct iio_trigger *trig)
        __module_get(trig->ops->owner);
 }
 
+/**
+ * iio_device_set_drvdata() - Set trigger driver data
+ * @trig: IIO trigger structure
+ * @data: Driver specific data
+ *
+ * Allows to attach an arbitrary pointer to an IIO trigger, which can later be
+ * retrieved by iio_trigger_get_drvdata().
+ */
+static inline void iio_trigger_set_drvdata(struct iio_trigger *trig, void *data)
+{
+       trig->private_data = data;
+}
+
+/**
+ * iio_trigger_get_drvdata() - Get trigger driver data
+ * @trig: IIO trigger structure
+ *
+ * Returns the data previously set with iio_trigger_set_drvdata()
+ */
+static inline void *iio_trigger_get_drvdata(struct iio_trigger *trig)
+{
+       return trig->private_data;
+}
+
 /**
  * iio_trigger_register() - register a trigger with the IIO core
  * @trig_info: trigger to be registered