Kernal Configuration Part XXV

Kernel Configuration - Part XXV

Character devices, block devices, input core support, IDE/ATAPI, RAID, SCSI.
Sometimes the Linux kernel can be a swirling array of device types and acronyms.

But if you approach your kernel configuration one element at a time, the mystery

will disappear piece by piece.

Today’s kernel configuration topic is character devices. We’ve talked several
times in Penguin Shell about the different device types in Linux. Among them are

block and character devices. Remember that block devices cache data and write it

in a series of bursts or blocks. Character devices, on the other hand, receive
data “on the fly,” in a manner that’s more along the lines of streaming. If you
think of data in terms of single characters, block devices receive data in
multi-character chunks, while character devices take that same data one
character at a time.

Most systems utilize four main character devices. Monitors, keyboards, mice, and

any device attached to a serial port comprise the main character device types.
As with all other devices, these are just general groups. Manufacturers tend to
utilize unique or moderately modified protocols for communicating with and
operating these devices. In other words, a Logitech mouse and a Microsoft
Intellimouse operate a bit differently, even though they may both interface with

a PS/2 or USB port.

And, as with the other kernel configuration parameters, you’ll want to select
the specifics of your particular hardware when configuring character devices.
There are many options in the character device section for a reason - there are
many options in the hardware itself.

Character device support does have a bit more meaning in Linux when using X
Window. If you look back at the main character device types, you’ll see that
most will, to one degree or another, be tied directly into the operation of X
Window. While X Window functions as a separate entity from the kernel - you can
operate a fully-functional system without X Window - the basic drivers and
protocols for using these devices will need to be in place in the kernel.
Accordingly, it’s worth taking a bit of extra time and care when choosing
devices and options in the character device kernel configuration section.

Monday, we’ll move on to kernel level multimedia device support.