Difference between revisions of "Zephyr device driver model"

Revision as of 05:50, 13 August 2021

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.