Linux Device Drivers

Drivers

There is little to say at this point about the Linux drivers directory. The source files in this directory have been referenced throughout the book; that’s why I left them until last in this walk through the source tree.

Char, Block, and Network Drivers

Although most of the drivers in these directories are specific to a particular hardware device, a few of the files play a more general role in the system’s setup.

As far as drivers/char is concerned, code that implements the N_TTY line discipline is implemented there. N_TTY is the default line discipline for system ttys, and it is defined in n_tty.c. Another device-independent file in drivers/char is misc.c, which provides support for ``misc'' devices. A ``misc'' device is a simplified char driver that has a single minor number.

This directory also includes console support for PCs and some other architecture-dependent drivers; it actually contains a miscellaneous assortment of files that didn’t fit elsewhere.

drivers/block is much cleaner. It includes single-file drivers for most block devices and the full-featured IDE driver, which is split into multiple files. Several files in this directory provide general-purpose support; genhd.c handles partition tables and ll_rw_block.c is in charge of the low-level mechanism for data transfer to and from the physical device. The request structure is the main player in ll_rw_block.c.

drivers/net contains a long list of drivers for PC network cards, plus a few for other architectures ...