Specialized Device Drivers
All device drivers that are accessible to application logic are
either: (1) Character device drivers that can be accessed via the
standard driver operations (open(), close(), read(),
write(), etc.), or (2) block drivers that can be accessing
only as part of mounting a file system or other special use cases
as described in the preceding paragraph.
In addition to this, there are also specialized “drivers” that can be used only within the OS logic itself and are not accessible to application logic. These specialized drivers are discussed in the following section.
Note
While special drivers are internal, in some cases there are also character/block drivers that sit on top of these special drivers and thus expose them to applications.