cros_ec_sensorhub registers a listener and query motion sense FIFO,
spread to iio sensors registers.

To test, we can use libiio:
iiod&
iio_readdev -u ip:localhost -T 10000 -s 25 -b 16 cros-ec-gyro | od -x

Signed-off-by: Gwendal Grignou <gwen...@chromium.org>
---
Changes sunce v2:
- Do not register a .remove routinge in plaform_driver. A
  devm_action_add is added later patch IIO driver register their
callback.
- Remove double lines, add lines before return calls.
- Handle FLUSH flag from EC.
- Use ktime_t for most timestamp measurements.
- Add doxygen comments
- Cleanup timestamp collection when processing FIFO.
- Rename fifo_toggle to fifo_enable

 drivers/platform/chrome/Makefile              |   3 +-
 drivers/platform/chrome/cros_ec_sensorhub.c   | 123 ++++--
 .../platform/chrome/cros_ec_sensorhub_ring.c  | 412 ++++++++++++++++++
 .../linux/platform_data/cros_ec_sensorhub.h   |  77 ++++
 4 files changed, 583 insertions(+), 32 deletions(-)
 create mode 100644 drivers/platform/chrome/cros_ec_sensorhub_ring.c

diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index a164c40dc0996..cb709048c003e 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -17,7 +17,8 @@ obj-$(CONFIG_CROS_EC_PROTO)           += cros_ec_proto.o 
cros_ec_trace.o
 obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)   += cros_kbd_led_backlight.o
 obj-$(CONFIG_CROS_EC_CHARDEV)          += cros_ec_chardev.o
 obj-$(CONFIG_CROS_EC_LIGHTBAR)         += cros_ec_lightbar.o
-obj-$(CONFIG_CROS_EC_SENSORHUB)                += cros_ec_sensorhub.o
+cros_ec_sensorsupport-objs                     := cros_ec_sensorhub_ring.o 
cros_ec_sensorhub.o
+obj-$(CONFIG_CROS_EC_SENSORHUB)                += cros_ec_sensorsupport.o
 obj-$(CONFIG_CROS_EC_VBC)              += cros_ec_vbc.o
 obj-$(CONFIG_CROS_EC_DEBUGFS)          += cros_ec_debugfs.o
 obj-$(CONFIG_CROS_EC_SYSFS)            += cros_ec_sysfs.o
diff --git a/drivers/platform/chrome/cros_ec_sensorhub.c 
b/drivers/platform/chrome/cros_ec_sensorhub.c
index 5fea4c28c5c95..87308dadc32c5 100644
--- a/drivers/platform/chrome/cros_ec_sensorhub.c
+++ b/drivers/platform/chrome/cros_ec_sensorhub.c
@@ -24,7 +24,6 @@
 
 #define DRV_NAME               "cros-ec-sensorhub"
 
-
 static struct device_type cros_ec_sensorhub_dev_type = {
        .name   = "cros_ec_iio_sensor",
 };
@@ -64,14 +63,13 @@ static int cros_ec_sensorhub_allocate_single_sensor(
 }
 
 static int cros_ec_sensorhub_register(struct device *dev,
-               struct cros_ec_dev *ec)
+               struct cros_ec_sensorhub *sensorhub)
 {
        int ret, i, id, sensor_num;
        int sensor_type[MOTIONSENSE_TYPE_MAX] = { 0 };
-       struct ec_params_motion_sense *params;
-       struct ec_response_motion_sense *resp;
-       struct cros_ec_command *msg;
        char *name;
+       struct cros_ec_command *msg = sensorhub->msg;
+       struct cros_ec_dev *ec = sensorhub->ec;
 
        sensor_num = cros_ec_get_sensor_count(ec);
        if (sensor_num < 0) {
@@ -86,32 +84,21 @@ static int cros_ec_sensorhub_register(struct device *dev,
                return -EINVAL;
        }
 
-       /* Prepare a message to send INFO command to each sensor. */
-       msg = kzalloc(sizeof(struct cros_ec_command) +
-                     max(sizeof(*params), sizeof(*resp)), GFP_KERNEL);
-       if (!msg) {
-               ret = -ENOMEM;
-               goto error;
-       }
-
        msg->version = 1;
-       msg->command = EC_CMD_MOTION_SENSE_CMD + ec->cmd_offset;
-       msg->outsize = sizeof(*params);
-       msg->insize = sizeof(*resp);
-       params = (struct ec_params_motion_sense *)msg->data;
-       resp = (struct ec_response_motion_sense *)msg->data;
+       msg->insize = sizeof(struct ec_response_motion_sense);
+       msg->outsize = sizeof(struct ec_params_motion_sense);
 
        id = 0;
        for (i = 0; i < sensor_num; i++) {
-               params->cmd = MOTIONSENSE_CMD_INFO;
-               params->info.sensor_num = i;
+               sensorhub->params->cmd = MOTIONSENSE_CMD_INFO;
+               sensorhub->params->info.sensor_num = i;
                ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
                if (ret < 0) {
                        dev_warn(dev, "no info for EC sensor %d : %d/%d\n",
                                 i, ret, msg->result);
                        continue;
                }
-               switch (resp->info.type) {
+               switch (sensorhub->resp->info.type) {
                case MOTIONSENSE_TYPE_ACCEL:
                        name = "cros-ec-accel";
                        break;
@@ -134,14 +121,15 @@ static int cros_ec_sensorhub_register(struct device *dev,
                        name = "cros-ec-activity";
                        break;
                default:
-                       dev_warn(dev, "unknown type %d\n", resp->info.type);
+                       dev_warn(dev, "unknown type %d\n",
+                                sensorhub->resp->info.type);
                        continue;
                }
                ret = cros_ec_sensorhub_allocate_single_sensor(dev, name, i);
                if (ret)
-                       goto error;
+                       return ret;
 
-               sensor_type[resp->info.type]++;
+               sensor_type[sensorhub->resp->info.type]++;
        }
 
        if (sensor_type[MOTIONSENSE_TYPE_ACCEL] >= 2)
@@ -152,9 +140,6 @@ static int cros_ec_sensorhub_register(struct device *dev,
                ret = cros_ec_sensorhub_allocate_single_sensor(
                                dev, "cros-ec-lid-angle", 0);
        }
-
-error:
-       kfree(msg);
        return ret;
 }
 
@@ -163,34 +148,110 @@ static int cros_ec_sensorhub_probe(struct 
platform_device *pdev)
        struct device *dev = &pdev->dev;
        struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
        int ret;
-       struct cros_ec_sensorhub *data =
-               kzalloc(sizeof(struct cros_ec_sensorhub), GFP_KERNEL);
+       struct cros_ec_sensorhub *data;
+       struct cros_ec_command *msg;
 
+       msg = devm_kzalloc(dev, sizeof(struct cros_ec_command) +
+                       max((u16)sizeof(struct ec_params_motion_sense),
+                           ec->ec_dev->max_response), GFP_KERNEL);
+       if (!msg)
+               return -ENOMEM;
+       msg->command = EC_CMD_MOTION_SENSE_CMD + ec->cmd_offset;
+
+       data = devm_kzalloc(dev, sizeof(struct cros_ec_sensorhub), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
 
+       data->dev = dev;
        data->ec = ec;
+
+       mutex_init(&data->cmd_lock);
+       data->msg = msg;
+       data->params = (struct ec_params_motion_sense *)msg->data;
+       data->resp = (struct ec_response_motion_sense *)msg->data;
+
        dev_set_drvdata(dev, data);
 
        /* Check whether this EC is a sensor hub. */
        if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE)) {
-               ret = cros_ec_sensorhub_register(dev, ec);
+               ret = cros_ec_sensorhub_register(dev, data);
        } else {
                ret = cros_ec_sensorhub_allocate_single_sensor(
                                dev, "cros-ec-accel-legacy", 0);
                ret |= cros_ec_sensorhub_allocate_single_sensor(
                                dev, "cros-ec-accel-legacy", 1);
        }
-       if (ret)
+       if (ret) {
                dev_err(dev, "failed to add EC sensors: error %d\n", ret);
+               return ret;
+       }
+
+       /*
+        * If the EC does not have a FIFO, the sensors will query their data
+        * themselves via sysfs or a software trigger.
+        */
+       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO)) {
+               ret = cros_ec_sensorhub_ring_add(data);
+               /*
+                * The msg and its data is not under the control of the ring
+                * handler.
+                */
+       }
        return ret;
 }
 
+static int cros_ec_sensorhub_remove(struct platform_device *pdev)
+{
+       struct cros_ec_sensorhub *sensorhub = platform_get_drvdata(pdev);
+       struct cros_ec_dev *ec = sensorhub->ec;
+
+       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO))
+               cros_ec_sensorhub_ring_remove(sensorhub);
+       return 0;
+}
+
+/*
+ * When the EC is suspending, we must stop sending interrupt,
+ * we may use the same interrupt line for waking up the device.
+ * Tell the EC to stop sending non-interrupt event on the iio ring.
+ */
+static int __maybe_unused cros_ec_ring_prepare(struct device *dev)
+{
+       struct platform_device *pdev = to_platform_device(dev);
+       struct cros_ec_sensorhub *sensorhub = platform_get_drvdata(pdev);
+       struct cros_ec_dev *ec = sensorhub->ec;
+
+       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO))
+               return cros_ec_sensorhub_ring_fifo_enable(sensorhub, false);
+       return 0;
+}
+
+static void __maybe_unused cros_ec_ring_complete(struct device *dev)
+{
+       struct platform_device *pdev = to_platform_device(dev);
+       struct cros_ec_sensorhub *sensorhub = platform_get_drvdata(pdev);
+       struct cros_ec_dev *ec = sensorhub->ec;
+
+       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO))
+               cros_ec_sensorhub_ring_fifo_enable(sensorhub, true);
+}
+
+#if CONFIG_PM_SLEEP
+static const struct dev_pm_ops cros_ec_sensorhub_ring_pm_ops = {
+       .prepare = cros_ec_ring_prepare,
+       .complete = cros_ec_ring_complete
+};
+#else
+static const struct dev_pm_ops cros_ec_sensorhub_ring_pm_ops = { };
+#endif
+
 static struct platform_driver cros_ec_sensorhub_driver = {
        .driver = {
                .name = DRV_NAME,
+               .pm = &cros_ec_sensorhub_ring_pm_ops,
        },
        .probe = cros_ec_sensorhub_probe,
+       .remove = cros_ec_sensorhub_remove,
 };
 
 module_platform_driver(cros_ec_sensorhub_driver);
diff --git a/drivers/platform/chrome/cros_ec_sensorhub_ring.c 
b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
new file mode 100644
index 0000000000000..caf4b02d5e345
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
@@ -0,0 +1,412 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * cros_ec_sensorhub_ring - Driver for Chrome OS EC Sensor hub FIFO.
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/module.h>
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/platform_data/cros_ec_sensorhub.h>
+#include <linux/platform_device.h>
+#include <linux/sort.h>
+#include <linux/slab.h>
+
+static inline int cros_sensorhub_send_sample(
+               struct cros_ec_sensorhub *sensorhub,
+               struct cros_ec_sensors_ring_sample *sample)
+{
+       int id = sample->sensor_id;
+       cros_ec_sensorhub_push_data_cb_t cb;
+       struct iio_dev *indio_dev;
+
+       if (id > CROS_EC_SENSOR_MAX)
+               return -EINVAL;
+
+       cb = sensorhub->push_data[id].push_data_cb;
+       if (!cb)
+               return 0;
+
+       indio_dev = sensorhub->push_data[id].indio_dev;
+
+       if (sample->flag & MOTIONSENSE_SENSOR_FLAG_FLUSH)
+               return 0;
+
+       return cb(indio_dev, sample->vector, sample->timestamp);
+}
+
+/**
+ * Function to register the callback to the sensor hub.
+ * The callback cb will be used by cros_ec_sensorhub_ring to distribute events
+ * from the EC.
+ * @sensor_hub : Sensor Hub object
+ * @sensor_num : The sensor the caller is interested in.
+ * @indio_dev : The iio device to use when a sample arrives.
+ * @cb : The callback to call when a sample arrives.
+ */
+int cros_ec_sensorhub_register_push_data(
+               struct cros_ec_sensorhub *sensorhub,
+               u8 sensor_num,
+               struct iio_dev *indio_dev,
+               cros_ec_sensorhub_push_data_cb_t cb)
+{
+       if (sensor_num > CROS_EC_SENSOR_MAX)
+               return -EINVAL;
+       if (sensorhub->push_data[sensor_num].indio_dev != NULL)
+               return -EINVAL;
+
+       sensorhub->push_data[sensor_num].indio_dev = indio_dev;
+       sensorhub->push_data[sensor_num].push_data_cb = cb;
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(cros_ec_sensorhub_register_push_data);
+
+void cros_ec_sensorhub_unregister_push_data(
+               struct cros_ec_sensorhub *sensorhub,
+               u8 sensor_num)
+{
+       sensorhub->push_data[sensor_num].indio_dev = NULL;
+       sensorhub->push_data[sensor_num].push_data_cb = NULL;
+}
+EXPORT_SYMBOL_GPL(cros_ec_sensorhub_unregister_push_data);
+
+/**
+ * Enable or disable interrupt generation for FIFO events.
+ * To be called before sleeping or when noone is listening.
+ * @sensor_hub : Sensor Hub object
+ * @on : true when events are requested.
+ */
+int cros_ec_sensorhub_ring_fifo_enable(
+               struct cros_ec_sensorhub *sensorhub,
+               bool on)
+{
+       int ret;
+
+       mutex_lock(&sensorhub->cmd_lock);
+       sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INT_ENABLE;
+       sensorhub->params->fifo_int_enable.enable = on;
+
+       sensorhub->msg->outsize = sizeof(struct ec_params_motion_sense);
+       sensorhub->msg->insize = sizeof(struct ec_response_motion_sense);
+
+       ret = cros_ec_cmd_xfer_status(sensorhub->ec->ec_dev, sensorhub->msg);
+       /* We expect to receive a payload of 4 bytes, ignore. */
+       if (ret > 0)
+               ret = 0;
+       mutex_unlock(&sensorhub->cmd_lock);
+
+       return ret;
+}
+
+/**
+ * cros_ec_ring_process_event: process one EC FIFO event
+ *
+ * Process one EC event, add it in the ring if necessary.
+ *
+ * @sensorhub: Sensorhub object.
+ * @fifo_info: fifo information from the EC (includes b point, EC timebase).
+ * @fifo_timestamp: EC IRQ, kernel timebase (aka c)
+ * @current_timestamp: calculated event timestamp, kernel timebase (aka a')
+ * @in: incoming FIFO event from EC (includes a point, EC timebase)
+ * @out: outgoing event to user space (includes a')
+ *
+ * Return true if out event has been populated.
+ */
+static bool cros_ec_ring_process_event(
+                               struct cros_ec_sensorhub *sensorhub,
+                               const struct cros_ec_fifo_info *fifo_info,
+                               const ktime_t fifo_timestamp,
+                               ktime_t *current_timestamp,
+                               struct ec_response_motion_sensor_data *in,
+                               struct cros_ec_sensors_ring_sample *out)
+{
+       int axis;
+       /* Do not populate the filter based on asynchronous events. */
+       const int async_flags = in->flags &
+               (MOTIONSENSE_SENSOR_FLAG_ODR | MOTIONSENSE_SENSOR_FLAG_FLUSH);
+       const s64 now = cros_ec_get_time_ns();
+
+       if (in->flags & MOTIONSENSE_SENSOR_FLAG_TIMESTAMP && !async_flags) {
+               s64 a = in->timestamp;
+               s64 b = fifo_info->info.timestamp;
+               s64 c = fifo_timestamp;
+               s64 new_timestamp;
+
+               /*
+                * disable filtering since we might add more jitter
+                * if b is in a random point in time
+                */
+               new_timestamp = c - b * 1000 + a * 1000;
+
+               /*
+                * The timestamp can be stale if we had to use the fifo
+                * info timestamp.
+                */
+               if (new_timestamp - *current_timestamp > 0)
+                       *current_timestamp = new_timestamp;
+       }
+
+       if (in->flags & MOTIONSENSE_SENSOR_FLAG_FLUSH) {
+               out->sensor_id = in->sensor_num;
+               out->timestamp = *current_timestamp;
+               out->flag = in->flags;
+               /*
+                * No other payload information provided with
+                * flush ack.
+                */
+               return true;
+       }
+       if (in->flags & MOTIONSENSE_SENSOR_FLAG_TIMESTAMP)
+               /* If we just have a timestamp, skip this entry. */
+               return false;
+
+       /* Regular sample */
+       out->sensor_id = in->sensor_num;
+       if (*current_timestamp - now > 0) {
+               /* If the timestamp is in the future. */
+               out->timestamp = now;
+       } else {
+               out->timestamp = *current_timestamp;
+       }
+
+       out->flag = in->flags;
+       for (axis = 0; axis < 3; axis++)
+               out->vector[axis] = in->data[axis];
+
+       return true;
+}
+
+/*
+ * cros_ec_sensorhub_ring_handler - the trigger handler function
+ *
+ * @sensorhub: device information.
+ *
+ * Called by the notifier, process the EC sensor FIFO queue.
+ */
+static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
+{
+       struct cros_ec_fifo_info *fifo_info = &sensorhub->fifo_info;
+       struct cros_ec_dev *ec = sensorhub->ec;
+       ktime_t fifo_timestamp, current_timestamp;
+       int i, j, number_data, ret;
+       unsigned long sensor_mask = 0;
+       struct ec_response_motion_sensor_data *in;
+       struct cros_ec_sensors_ring_sample *out, *last_out;
+
+       mutex_lock(&sensorhub->cmd_lock);
+
+       /* Get FIFO information if there are lost vectors. */
+       if (fifo_info->info.total_lost) {
+               /* Need to retrieve the number of lost vectors per sensor */
+               sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INFO;
+               sensorhub->msg->outsize = 1;
+               sensorhub->msg->insize =
+                       sizeof(struct ec_response_motion_sense_fifo_info) +
+                       sizeof(u16) * CROS_EC_SENSOR_MAX;
+
+               if (cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg) < 0) {
+                       mutex_unlock(&sensorhub->cmd_lock);
+                       return;
+               }
+               memcpy(fifo_info, &sensorhub->resp->fifo_info,
+                      sizeof(*fifo_info));
+
+               /*
+                * Update collection time, will not be as precise as the
+                * non-error case.
+                */
+               fifo_timestamp = cros_ec_get_time_ns();
+       } else {
+               fifo_timestamp = sensorhub->fifo_timestamp[
+                       CROS_EC_SENSOR_NEW_TS];
+       }
+
+       if (fifo_info->info.count > sensorhub->fifo_size ||
+           fifo_info->info.size != sensorhub->fifo_size) {
+               dev_warn(sensorhub->dev,
+                        "Mismatch EC data: count %d, size %d - expected %d",
+                        fifo_info->info.count, fifo_info->info.size,
+                        sensorhub->fifo_size);
+               mutex_unlock(&sensorhub->cmd_lock);
+               return;
+       }
+
+
+       /* Copy elements in the main fifo */
+       current_timestamp = sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS];
+       out = sensorhub->ring;
+       for (i = 0; i < fifo_info->info.count; i += number_data) {
+               sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_READ;
+               sensorhub->params->fifo_read.max_data_vector =
+                       fifo_info->info.count - i;
+               sensorhub->msg->outsize =
+                       sizeof(struct ec_params_motion_sense);
+               sensorhub->msg->insize =
+                       sizeof(sensorhub->resp->fifo_read) +
+                       sensorhub->params->fifo_read.max_data_vector *
+                         sizeof(struct ec_response_motion_sensor_data);
+               ret = cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg);
+               if (ret < 0) {
+                       dev_warn(sensorhub->dev, "Fifo error: %d\n", ret);
+                       break;
+               }
+               number_data = sensorhub->resp->fifo_read.number_data;
+               if (number_data == 0) {
+                       dev_dbg(sensorhub->dev, "Unexpected empty FIFO\n");
+                       break;
+               }
+               if (number_data > fifo_info->info.count - i) {
+                       dev_warn(sensorhub->dev,
+                                "Invalid EC data: too many entry received: %d, 
expected %d",
+                                number_data, fifo_info->info.count - i);
+                       break;
+               }
+               if (out + number_data >
+                   sensorhub->ring + fifo_info->info.count) {
+                       dev_warn(sensorhub->dev,
+                                "Too many samples: %d (%zd data) to %d entries 
for expected %d entries",
+                                i, out - sensorhub->ring, i + number_data,
+                                fifo_info->info.count);
+                       break;
+               }
+
+               for (in = sensorhub->resp->fifo_read.data, j = 0;
+                    j < number_data; j++, in++) {
+                       if (cros_ec_ring_process_event(
+                                       sensorhub, fifo_info, fifo_timestamp,
+                                       &current_timestamp, in, out)) {
+                               sensor_mask |= (1 << in->sensor_num);
+                               out++;
+                       }
+               }
+       }
+       mutex_unlock(&sensorhub->cmd_lock);
+       last_out = out;
+
+       if (out == sensorhub->ring)
+               /* Unexpected empty FIFO. */
+               goto ring_handler_end;
+
+       /*
+        * Check if current_timestamp is ahead of the last sample.
+        * Normally, the EC appends a timestamp after the last sample, but if
+        * the AP is slow to respond to the IRQ, the EC may have added new
+        * samples. Use the FIFO info timestamp as last timestamp then.
+        */
+       if ((last_out-1)->timestamp == current_timestamp)
+               current_timestamp = fifo_timestamp;
+
+       /* Warn on lost samples. */
+       for_each_set_bit(i, &sensor_mask, BITS_PER_LONG) {
+               if (fifo_info->info.total_lost) {
+                       int lost = fifo_info->lost[i];
+
+                       if (lost) {
+                               dev_warn_ratelimited(sensorhub->dev,
+                                       "Sensor %d: lost: %d out of %d\n", i,
+                                       lost, fifo_info->info.total_lost);
+                       }
+               }
+       }
+
+       /* push the event into the kfifo */
+       for (out = sensorhub->ring; out < last_out; out++)
+               cros_sensorhub_send_sample(sensorhub, out);
+
+ring_handler_end:
+       sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] = current_timestamp;
+}
+
+static int cros_ec_sensorhub_event(struct notifier_block *nb,
+       unsigned long queued_during_suspend, void *_notify)
+{
+       struct cros_ec_sensorhub *sensorhub;
+       struct cros_ec_device *ec_dev;
+
+       sensorhub = container_of(nb, struct cros_ec_sensorhub, notifier);
+       ec_dev = sensorhub->ec->ec_dev;
+
+       if (ec_dev->event_data.event_type != EC_MKBP_EVENT_SENSOR_FIFO)
+               return NOTIFY_DONE;
+
+       if (ec_dev->event_size != sizeof(ec_dev->event_data.data.sensor_fifo)) {
+               dev_warn(ec_dev->dev, "Invalid fifo info size\n");
+               return NOTIFY_DONE;
+       }
+
+       if (queued_during_suspend)
+               return NOTIFY_OK;
+
+       sensorhub->fifo_info.info = ec_dev->event_data.data.sensor_fifo.info;
+       sensorhub->fifo_timestamp[CROS_EC_SENSOR_NEW_TS] =
+               ec_dev->last_event_time;
+       cros_ec_sensorhub_ring_handler(sensorhub);
+
+       return NOTIFY_OK;
+}
+
+/**
+ * Add/Remove the fifo functionality if the EC supports it.
+ * @sensor_hub : Sensor Hub object
+ */
+int cros_ec_sensorhub_ring_add(struct cros_ec_sensorhub *sensorhub)
+{
+       struct cros_ec_dev *ec = sensorhub->ec;
+       int ret;
+
+       /* Retrieve FIFO information */
+       sensorhub->msg->version = 2;
+       sensorhub->params->cmd = MOTIONSENSE_CMD_FIFO_INFO;
+       sensorhub->msg->outsize = 1;
+       sensorhub->msg->insize =
+               sizeof(struct ec_response_motion_sense_fifo_info) +
+               sizeof(u16) * CROS_EC_SENSOR_MAX;
+
+       ret = cros_ec_cmd_xfer_status(ec->ec_dev, sensorhub->msg);
+       if (ret < 0)
+               return ret;
+
+       /*
+        * Allocate the full fifo.
+        * We need to copy the whole FIFO to set timestamps properly *
+        */
+       sensorhub->fifo_size = sensorhub->resp->fifo_info.size;
+       sensorhub->ring = devm_kcalloc(sensorhub->dev, sensorhub->fifo_size,
+                       sizeof(*sensorhub->ring), GFP_KERNEL);
+       if (!sensorhub->ring)
+               return -ENOMEM;
+
+       sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] =
+               cros_ec_get_time_ns();
+
+       /* register the notifier that will act as a top half interrupt. */
+       sensorhub->notifier.notifier_call = cros_ec_sensorhub_event;
+       ret = blocking_notifier_chain_register(&ec->ec_dev->event_notifier,
+                                              &sensorhub->notifier);
+       if (ret < 0) {
+               dev_warn(sensorhub->dev, "failed to register notifier\n");
+               return ret;
+       }
+
+       /* Start collection samples. */
+       return cros_ec_sensorhub_ring_fifo_enable(sensorhub, true);
+}
+
+int cros_ec_sensorhub_ring_remove(struct cros_ec_sensorhub *sensorhub)
+{
+       struct cros_ec_device *ec_dev = sensorhub->ec->ec_dev;
+
+       /* Disable the ring, prevent EC interrupt to the AP for nothing. */
+       cros_ec_sensorhub_ring_fifo_enable(sensorhub, false);
+       blocking_notifier_chain_unregister(&ec_dev->event_notifier,
+                                          &sensorhub->notifier);
+
+       return 0;
+}
diff --git a/include/linux/platform_data/cros_ec_sensorhub.h 
b/include/linux/platform_data/cros_ec_sensorhub.h
index c18fba660bb62..595d010b58d95 100644
--- a/include/linux/platform_data/cros_ec_sensorhub.h
+++ b/include/linux/platform_data/cros_ec_sensorhub.h
@@ -8,6 +8,7 @@
 #ifndef __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H
 #define __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H
 
+#include <linux/iio/iio.h>
 #include <linux/platform_data/cros_ec_commands.h>
 
 /**
@@ -18,12 +19,88 @@ struct cros_ec_sensor_platform {
        u8 sensor_num;
 };
 
+/**
+ * Callback function to send datum to specific sensors.
+ * @indio_dev: The IIO device that will process the sample.
+ * @data: vector array of the ring sample.
+ * @timestamp: Timestamp in host timespace when the sample was acquired by
+ *             the EC.
+ */
+typedef int (*cros_ec_sensorhub_push_data_cb_t)(
+               struct iio_dev *indio_dev,
+               s16 *data,
+               s64 timestamp);
+
+struct cros_ec_sensorhub_sensor_push_data {
+       struct iio_dev *indio_dev;
+       cros_ec_sensorhub_push_data_cb_t push_data_cb;
+};
+
+enum {
+       CROS_EC_SENSOR_LAST_TS,
+       CROS_EC_SENSOR_NEW_TS,
+       CROS_EC_SENSOR_ALL_TS
+};
+
+#define CROS_EC_SENSOR_MAX 16
+
+struct __ec_todo_packed cros_ec_fifo_info {
+       struct ec_response_motion_sense_fifo_info info;
+       uint16_t lost[CROS_EC_SENSOR_MAX];
+};
+
+struct cros_ec_sensors_ring_sample {
+       uint8_t sensor_id;
+       uint8_t flag;
+       int16_t  vector[3];
+       s64      timestamp;
+} __packed;
+
 /*
  * struct cros_ec_sensorhub - Sensor Hub device data.
  */
 struct cros_ec_sensorhub {
+       /* Device object, mostly used for logging. */
+       struct device *dev;
+
        /* Embedded Controller where the hub is located. */
        struct cros_ec_dev *ec;
+
+       /* Structure to send FIFO requests. */
+       struct cros_ec_command *msg;
+       struct ec_params_motion_sense *params;
+       struct ec_response_motion_sense *resp;
+       struct mutex cmd_lock;
+
+       /* Notifier to kick the FIFO interrupt */
+       struct notifier_block notifier;
+
+       /* Preprocessed ring to send to kfifos */
+       struct cros_ec_sensors_ring_sample *ring;
+
+       ktime_t fifo_timestamp[CROS_EC_SENSOR_ALL_TS];
+       struct cros_ec_fifo_info fifo_info;
+       int    fifo_size;
+
+       /*
+        * Dynamic array to be able to spread datum to iio sensor objects.
+        */
+       struct cros_ec_sensorhub_sensor_push_data push_data[CROS_EC_SENSOR_MAX];
 };
 
+int cros_ec_sensorhub_register_push_data(
+               struct cros_ec_sensorhub *sensor_hub,
+               u8 sensor_num,
+               struct iio_dev *indio_dev,
+               cros_ec_sensorhub_push_data_cb_t cb);
+void cros_ec_sensorhub_unregister_push_data(
+               struct cros_ec_sensorhub *sensor_hub,
+               u8 sensor_num);
+
+int cros_ec_sensorhub_ring_add(struct cros_ec_sensorhub *sensor_hub);
+int cros_ec_sensorhub_ring_remove(struct cros_ec_sensorhub *sensor_hub);
+int cros_ec_sensorhub_ring_fifo_enable(
+               struct cros_ec_sensorhub *sensorhub,
+               bool on);
+
 #endif   /* __LINUX_PLATFORM_DATA_CROS_EC_SENSORHUB_H */
-- 
2.23.0.866.gb869b98d4c-goog

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