Driver Code Layout
The code for a device driver is usually divided into the following
Header files provide the following definitions:
Data structures specific to the device, such as a structure representing the device registers
Data structures defined by the driver for maintaining state information
Defined constants, such as those representing the bits of the device registers
Macros, such as those defining the static mapping between the minor device number and the instance number
Some of the header file definitions, such as the state structure, might be
needed only by the device driver. This information should go in private
header files that are only included by the device driver itself.
Any information that an application might require, such as the I/O control commands,
should be in public header files. These files are included by the driver
and by any applications that need information about the device.
While there is no standard for naming private and public files, one convention
is to name the private header file xximpl.h and the public header
A C source file (a .c file) for a device driver has the
Contains the data declarations and the code for the entry points of the driver
Contains the #include statements that are needed by the driver
Declares extern references
Declares local data
Sets up the cb_ops and dev_ops structures
Declares and initializes the module configuration section, that is, the modlinkage(9S) and modldrv(9S) structures
Makes any other necessary declarations
Defines the driver entry points
In general, the configuration file for a driver defines all of the properties
that the driver needs. Entries in the driver configuration file specify possible device
instances that the driver can probe for existence. Driver global properties can be
set in the driver's configuration file. See the driver.conf(4) man page for more
Driver configuration files are required for devices that are not self-identifying.
Driver configuration files are optional for self-identifying devices (SID). For self-identifying devices, the
configuration file can be used to add properties into SID nodes.
The following properties are examples of properties that are not set in the
driver configuration file:
Drivers that use the SBus peripheral bus generally get property information from the SBus card. In cases where additional properties are needed, the driver configuration file can contain properties that are defined by sbus(4).
The properties of a PCI bus can generally be derived from the PCI configuration space. In cases where private driver properties are needed, the driver configuration file can contain properties that are defined by pci(4).
Drivers on the ISA bus can use additional properties that are defined by isa(4).