Nowadays, almost all laptops, and even a number of desktops, contain PCMCIA slots. PCMCIA is an abbreviation for Personal Computer Memory Card International Association, a commission that defines standards for expansion cards^[5]. The PCMCIA itself was founded in 1990. It initially developed a set of standards by which memory could be added to portable systems. The PCMCIA specification 2.0 release in 1991 added protocols for I/O devices and hard disks. The 2.1 release in 1993 refined these specifications, and is the standard around which PCMCIA cards are built today. PCMCIA cards are credit card size adapters which fit into PCMCIA slots. There are three types of PCMCIA cards, Type I generally used for memory cards such as FLASH and STATIC RAM; Type II used for I/O peripherals such as serial adapters and fax-modems and Type III which are used for rotating media such as hard disks. The only difference in the physical specification for these cards is thickness: type I is the thinnest, type III the thickest.

PCMCIA cards are “hot pluggable” e.g. you can remove your network card without damaging your system (your network will not work of course) and plug it back in which will automatically start up your card and configure the card for your system. Linux supports PCMCIA standards. It features a daemon which monitors PCMCIA sockets to see if cards are removed or inserted (cardmgr), and runs scripts to configure the network into your system. Linux also features drivers for the various PCMCIA cards. These drivers are either part of the kernel distribution or are supplied via an additional package (Card Services for Linux).

The cardmgr daemon is responsible for monitoring PCMCIA sockets, loading client drivers when needed and running user-level scripts in response to card insertions and removals. It records its actions in the system log, but also uses beeps to signal card status changes. The tones of the beeps indicate success or failure of particular configuration steps. Two high beeps indicate that a card was identified and configured successfully. A high beep followed by a low beep indicates that a card was identified, but could not be configured for some reason. One low beep indicates that a card could not be identified. The cardmgr daemon configures cards based on a database of known card types kept in /etc/pcmcia/config. This file describes the various client drivers, then describes how to identify various cards and which driver(s) belong with which cards. The format of this file is described in the pcmcia(5) man page.

“Card Services for Linux” is a complete PCMCIA or “PC Card” support package. It includes a set of loadable kernel modules that implement a version of the Card Services applications-programming interface, a set of client drivers for specific cards and a card manager daemon that can respond to card insertion and removal events, loading and unloading drivers on demand. It supports “hot swapping” of most card types, so cards can be safely inserted and ejected at any time. The release includes drivers for a variety of ethernet cards, a driver for modem and serial port cards, several SCSI adapter drivers, a driver for ATA/IDE drive cards and memory-card drivers that should support most SRAM cards and some flash cards.

You'll need the kernel source to install pcmcia-cs, since the driver modules contain references to the kernel source files. Installing the pcmcia-cs package results in a number of modules in the /lib/modules/<your-kernel-version> directory.

The PCMCIA startup script recognizes several groups of startup options which are set via environment variables. Multiple options should be separated by spaces and enclosed in quotes. Placement of startup options depends on the Linux distribution used. They may be placed directly in the startup script or they may be kept in a separate option file. These are specific for various Linux distributions.

Card Services should automatically avoid allocating IO ports and interrupts already in use by other standard devices. It will also attempt to detect conflicts with unknown devices, but this is not completely reliable. In some cases, you may need to explicitly exclude resources for a device in /etc/pcmcia/config.opts.

As of kernel 2.4 PCMCIA support is integrated into the kernel - that is: the modules (drivers) are part of the kernel code distribution. You may want to try that first. However, in some situations the integrated support does not work. In many cases, you will still want to download and install “Card Services for Linux” (pcmcia-cs).

The cardctl command can be used to check the status of a socket or to see how it is configured. It can also be used to alter the configuration status of a card.

If you are running X, the cardinfo utility produces a graphical interface to most cardctl functions.