Zephyr device driver model
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Excerpt from Zephyr project drivers documentation:
-
Driver Data Structures
The device initialization macros populate some data structures at build time which are split into read-only and runtime-mutable parts. At a high level we have:
struct device {
const char *name;
const void *config;
const void *api;
void * const data;
};
Excerpt from file ~/ncs/zephyr/include/drivers/sensor.h:
382 /**
383 * @brief Set an attribute for a sensor
384 *
385 * @param dev Pointer to the sensor device
386 * @param chan The channel the attribute belongs to, if any. Some
387 * attributes may only be set for all channels of a device, depending on
388 * device capabilities.
389 * @param attr The attribute to set
390 * @param val The value to set the attribute to
391 *
392 * @return 0 if successful, negative errno code if failure.
393 */
394 __syscall int sensor_attr_set(const struct device *dev,
395 enum sensor_channel chan,
396 enum sensor_attribute attr,
397 const struct sensor_value *val);
398
399 static inline int z_impl_sensor_attr_set(const struct device *dev,
400 enum sensor_channel chan,
401 enum sensor_attribute attr,
402 const struct sensor_value *val)
403 {
404 const struct sensor_driver_api *api =
405 (const struct sensor_driver_api *)dev->api;
406
407 if (api->attr_set == NULL) {
408 return -ENOSYS;
409 }
410
411 return api->attr_set(dev, chan, attr, val);
412 }
413
From these two code excerpts the big question is, how is dev->api assigned in early configuring code for an I2C based sensor?
./include/drivers/sensor.h:61: SENSOR_CHAN_ACCEL_XYZ, . . . hmm, this is part of a large enumeration:
53 enum sensor_channel {
54 /** Acceleration on the X axis, in m/s^2. */
55 SENSOR_CHAN_ACCEL_X,
56 /** Acceleration on the Y axis, in m/s^2. */
57 SENSOR_CHAN_ACCEL_Y,
58 /** Acceleration on the Z axis, in m/s^2. */
59 SENSOR_CHAN_ACCEL_Z,
60 /** Acceleration on the X, Y and Z axes. */
61 SENSOR_CHAN_ACCEL_XYZ,
62 /** Angular velocity around the X axis, in radians/s. */
63 SENSOR_CHAN_GYRO_X,
64 /** Angular velocity around the Y axis, in radians/s. */
65 SENSOR_CHAN_GYRO_Y,
66 /** Angular velocity around the Z axis, in radians/s. */
67 SENSOR_CHAN_GYRO_Z,
68 /** Angular velocity around the X, Y and Z axes. */
69 SENSOR_CHAN_GYRO_XYZ,
.
.
.