.. SPDX-License-Identifier: CC-BY-SA-4.0

.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)

Device Driver Configuration
===========================

This section describes configuration options related to the device drivers.
Note that network device drivers are not covered by the following options.

.. index:: CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER

.. _CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER:

CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER
------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then a Clock Driver may be
    initialized during system initialization.

DESCRIPTION:
    In case this configuration option is defined, then **no** Clock Driver is
    initialized during system initialization.

NOTES:
    This configuration parameter is intended to prevent the common user error
    of using the Hello World example as the baseline for an application and
    leaving out a clock tick source.

    The application shall define exactly one of the following configuration options

    * :ref:`CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER`,

    * `CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`, or

    * :ref:`CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER`,

    otherwise a compile time error in the configuration file will occur.

.. index:: CONFIGURE_APPLICATION_EXTRA_DRIVERS

.. _CONFIGURE_APPLICATION_EXTRA_DRIVERS:

CONFIGURE_APPLICATION_EXTRA_DRIVERS
-----------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_EXTRA_DRIVERS``

OPTION TYPE:
    This configuration option is an initializer define.

DEFAULT VALUE:
    The default value is the empty list.

VALUE CONSTRAINTS:
    The value of this configuration option shall be a list of initializers for
    structures of type :c:type:`rtems_driver_address_table`.

DESCRIPTION:
    The value of this configuration option is used to initialize the Device
    Driver Table.

NOTES:
    The value of this configuration option is placed after the entries of other
    device driver configuration options.

    See :ref:`CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS` for an alternative
    placement of application device driver initializers.

.. index:: CONFIGURE_APPLICATION_NEEDS_ATA_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_ATA_DRIVER:

CONFIGURE_APPLICATION_NEEDS_ATA_DRIVER
--------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_ATA_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the ATA Driver is
    initialized during system initialization.

NOTES:
    Most BSPs do not include support for an ATA Driver.

    If this option is defined and the BSP does not have this device driver, then
    the user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER:

CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
----------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Clock Driver is
    initialized during system initialization.

NOTES:
    The Clock Driver is responsible for providing a regular interrupt
    which invokes a clock tick directive.

    The application shall define exactly one of the following configuration options

    * `CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER`,

    * :ref:`CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`, or

    * :ref:`CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER`,

    otherwise a compile time error in the configuration file will occur.

.. index:: CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Console Driver is
    initialized during system initialization.

NOTES:
    The Console Driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    BSPs should be constructed in a manner that allows :c:func:`printk` to work
    properly without the need for the Console Driver to be configured.

    The

    * :ref:`CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`,

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER`, and

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER`

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER:

CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER
-----------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_FRAME_BUFFER_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Frame Buffer Driver is
    initialized during system initialization.

NOTES:
    Most BSPs do not include support for a Frame Buffer Driver. This is
    because many boards do not include the required hardware.

    If this option is defined and the BSP does not have this device driver, then
    the user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_IDE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_IDE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_IDE_DRIVER
--------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_IDE_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the IDE Driver is
    initialized during system initialization.

NOTES:
    Most BSPs do not include support for an IDE Driver.

    If this option is defined and the BSP does not have this device driver, then
    the user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER
.. index:: /dev/null

.. _CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER:

CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_NULL_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the :file:`/dev/null`
    Driver is initialized during system initialization.

NOTES:
    This device driver is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER:

CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER
--------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_RTC_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Real-Time Clock Driver
    is initialized during system initialization.

NOTES:
    Most BSPs do not include support for a real-time clock (RTC). This is because
    many boards do not include the required hardware.

    If this is defined and the BSP does not have this device driver, then the
    user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER
-------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Simple Console Driver
    is initialized during system initialization.

NOTES:
    This device driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    This device driver reads via :c:func:`getchark`.

    This device driver writes via :c:func:`rtems_putc`.

    The Termios framework is not used.  There is no support to change device
    settings, e.g. baud, stop bits, parity, etc.

    The

    * :ref:`CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`,

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER`, and

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER`

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER:

CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER
------------------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Simple Task Console
    Driver is initialized during system initialization.

NOTES:
    This device driver is responsible for providing the :file:`/dev/console`
    device file.  This device is used to initialize the standard input, output,
    and error file descriptors.

    This device driver reads via :c:func:`getchark`.

    This device driver writes into a write buffer.  The count of characters
    written into the write buffer is returned.  It might be less than the
    requested count, in case the write buffer is full.  The write is
    non-blocking and may be called from interrupt context.  A dedicated task
    reads from the write buffer and outputs the characters via
    :c:func:`rtems_putc`.  This task runs with the least important priority.
    The write buffer size is 2047 characters and it is not configurable.

    Use ``fsync(STDOUT_FILENO)`` or ``fdatasync(STDOUT_FILENO)`` to drain the
    write buffer.

    The Termios framework is not used.  There is no support to change device
    settings, e.g.  baud, stop bits, parity, etc.

    The

    * :ref:`CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER`,

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_CONSOLE_DRIVER`, and

    * :ref:`CONFIGURE_APPLICATION_NEEDS_SIMPLE_TASK_CONSOLE_DRIVER`

    configuration options are mutually exclusive.

.. index:: CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER:

CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_STUB_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Stub Driver is
    initialized during system initialization.

NOTES:
    This device driver simply provides entry points that return successful and
    is primarily a test fixture. It is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER:

CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER
----------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Benchmark Timer Driver is
    initialized during system initialization.

NOTES:
    The Benchmark Timer Driver is intended for the benchmark tests of the RTEMS
    Testsuite.  Applications should not use this driver.

    The application shall define exactly one of the following configuration options

    * :ref:`CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER`,

    * :ref:`CONFIGURE_APPLICATION_DOES_NOT_NEED_CLOCK_DRIVER`, or

    * `CONFIGURE_APPLICATION_NEEDS_TIMER_DRIVER`,

    otherwise a compile time error will occur.

.. index:: CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER

.. _CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER:

CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER
-------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_WATCHDOG_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the Watchdog Driver is
    initialized during system initialization.

NOTES:
    Most BSPs do not include support for a watchdog device driver. This is
    because many boards do not include the required hardware.

    If this is defined and the BSP does not have this device driver, then the
    user will get a link time error for an undefined symbol.

.. index:: CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER
.. index:: /dev/zero

.. _CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER:

CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER
---------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_NEEDS_ZERO_DRIVER``

OPTION TYPE:
    This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:
    If this configuration option is undefined, then the described feature is not
    enabled.

DESCRIPTION:
    In case this configuration option is defined, then the :file:`/dev/zero`
    Driver is initialized during system initialization.

NOTES:
    This device driver is supported by all BSPs.

.. index:: CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS

.. _CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS:

CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS
------------------------------------------

CONSTANT:
    ``CONFIGURE_APPLICATION_PREREQUISITE_DRIVERS``

OPTION TYPE:
    This configuration option is an initializer define.

DEFAULT VALUE:
    The default value is the empty list.

VALUE CONSTRAINTS:
    The value of this configuration option shall be a list of initializers for
    structures of type :c:type:`rtems_driver_address_table`.

DESCRIPTION:
    The value of this configuration option is used to initialize the Device
    Driver Table.

NOTES:
    The value of this configuration option is placed after the entries defined by
    :ref:`CONFIGURE_BSP_PREREQUISITE_DRIVERS` and before all other device driver
    configuration options.

    See :ref:`CONFIGURE_APPLICATION_EXTRA_DRIVERS` for an alternative placement
    of application device driver initializers.

.. index:: CONFIGURE_ATA_DRIVER_TASK_PRIORITY

.. _CONFIGURE_ATA_DRIVER_TASK_PRIORITY:

CONFIGURE_ATA_DRIVER_TASK_PRIORITY
----------------------------------

CONSTANT:
    ``CONFIGURE_ATA_DRIVER_TASK_PRIORITY``

OPTION TYPE:
    This configuration option is an integer define.

DEFAULT VALUE:
    The default value is 140.

VALUE CONSTRAINTS:
    The value of this configuration option shall be a valid Classic API task
    priority.  The set of valid task priorities is scheduler-specific.

DESCRIPTION:
    The value of this configuration option defines the ATA task priority.

NOTES:
    This configuration option is only evaluated if the configuration option
    :ref:`CONFIGURE_APPLICATION_NEEDS_ATA_DRIVER` is defined.

.. index:: CONFIGURE_MAXIMUM_DRIVERS

.. _CONFIGURE_MAXIMUM_DRIVERS:

CONFIGURE_MAXIMUM_DRIVERS
-------------------------

CONSTANT:
    ``CONFIGURE_MAXIMUM_DRIVERS``

OPTION TYPE:
    This configuration option is an integer define.

DEFAULT VALUE:
    This is computed by default, and is set to the number of device drivers
    configured using the ``CONFIGURE_APPLICATIONS_NEEDS_XXX_DRIVER``
    configuration options.

VALUE CONSTRAINTS:
    The value of this configuration option shall satisfy all of the following
    constraints:

    * It shall be less than or equal to ``SIZE_MAX``.

    * It shall be greater than or equal than the number of statically configured
      device drivers.

    * It shall be less than or equal to a
      BSP-specific and application-specific value which depends on the size of the
      memory available to the application.

DESCRIPTION:
    The value of this configuration option defines the number of device drivers.

NOTES:
    If the application will dynamically install device drivers, then this
    configuration parameter shall be larger than the number of statically
    configured device drivers. Drivers configured using the
    ``CONFIGURE_APPLICATIONS_NEEDS_XXX_DRIVER`` configuration options are
    statically installed.
