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 configuration token for the class
 * 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 [source:trunk/mutekh/device/include/device/device.h device/include/device/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 `drivers/include/device/foobar.h`. It may contain

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

See [source:trunk/mutekh/drivers/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 [source:trunk/mutekh/drivers/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 [source:trunk/mutekh/drivers/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
}}}

= Add a configuration token for the class =

Edit [source:trunk/mutekh/drivers/device/drivers.config], add a configuration block for the class:
{{{
%config CONFIG_DRIVER_FOOBAR
flags nodefine
desc At least one foobar device driver must be enabled to have it defined
%config end
}}}

The `flags nodefine` statement tells the build system an user may not directly define this token,
and implies this token is only allowed to be provided by another one.

= 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`.

= Add a new driver =

See NewDriver