Adding a new driver class takes a few steps:

• Add the class in the class enumeration
• Add a header describing the class
  • its request functions
  • a structure containing pointer to request functions
  • utility function prototypes (blocking request wrappers, …) [1]
• Add reference to the class in the driver structure
• Add a directory for the class
• Add a C-file with utility functions [1]

[1]: This is only needed if the class has such utility functions.

In the examples, we'll call the new class foobar.

Adding the class in the device type enumeration

Edit hexo/include/hexo/device.h, you'll see a enum device_class_e. Add the new device type at the end.

    device_class_lcd,
    device_class_gpio,
    device_class_i2c,
+   device_class_foobar,
  };

Adding a header describing the class

Create a file in driver/include/device/foobar.h. It may contain

• Callback definitions,
• Request function prototypes,
• Global utility functions.

See trunk/mutekh/driver/include/device/char.h for sample file.

The struct dev_class_foobar_s is a structure holding all the class-specific request functions. You may ensure this structure holds less pointers than the DRV_MAX_FUNC_COUNT constant defined in trunk/mutekh/driver/include/device/driver.h.

Don't forget to protect the new header against circular inclusions with the lines:

#ifndef __DEVICE_FOOBAR_H__
#define __DEVICE_FOOBAR_H__

#endif

We'll use that macro later.

Adding a reference to the class in the driver structure

Edit trunk/mutekh/driver/include/device/driver.h and add an entry in the f union of the struct driver_s.

You must protect it with the macros defined in the header of the class, in case the class is not included in legacy code.

Dont #include your driver class in driver.h.

#ifdef __DEVICE_FOOBAR_H__
    struct dev_class_foobar_s foobar;
#endif

Create a directory for the class

• create a driver/device/foobar directory,
• add a Makefile inside it,
• add foobar in the list of subdirectories in driver/device/Makefile.

Create the global helper functions file for your class

• create a driver/device/foobar/device_foobar.c,
• add it in driver/device/foobar/Makefile.