Currently there are two PCMCIA systems — external PCMCIA and kernel PCMCIA. The external PCMCIA system by David Hinds is the older one. It is quite well tested and development of this type of PCMCIA system continues. The sources of the modules used are not integrated in the kernel sources, which is why it is called an external system.

Starting with kernel 2.4, a set of alternative modules is contained in the kernel sources forming the kernel PCMCIA system. The basic modules were written by Linus Torvalds. Their support of more recent CardBus bridges is better than with external PCMCIA.

Unfortunately, the two systems are not compatible. They contain different sets of card drivers. Depending on the hardware involved, only one of the systems may be suitable. The default in SUSE LINUX is the more recent kernel PCMCIA. It is possible to change the system, however. To do this, give the variable PCMCIA_SYSTEM in the file /etc/sysconfig/pcmcia either the value external or kernel. Then PCMCIA must be restarted with rcpcmcia restart. If intending to do just a temporary switch between systems, use rcpcmcia restart external or rcpcmcia restart kernel. If PCMCIA is not running, use the option start instead of restart to switch the PCMCIA system temporarily. Refer to /usr/share/doc/packages/pcmcia/README.SuSE for detailed information.

The kernel modules for both systems are located in the kernel packages. In addition, the packages pcmcia and hotplug are required. When PCMCIA is started, the modules pcmcia_core, i82365 (external PCMCIA) or yenta_socket (kernel PCMCIA), and ds are loaded. In some very rare cases, the module tcic is required instead of i82365 or yenta_socket. They initialize the existing PCMCIA controller and provide basic functionality.

As it is possible to change PCMCIA cards while the system is running, a deamon monitors any activity in the PCMCIA slots. Depending on the chosen PCMCIA system and hardware, this task is performed by the card manager or the hotplug system of the kernel. With external PCMCIA, only the card manager is used. For kernel PCMCIA, the card manager only handles PC Card cards. CardBus cards are handled by hotplug. The card manager is started by the PCMCIA start script after the base modules have been loaded. Because hotplug manages subsystems other than PCMCIA, it has its own start script.

If a card is inserted, card manager or hotplug determines the type and function of the card then loads the corresponding modules. If this is successful, card manager or hotplug starts certain initialization scripts. Depending on the function of the card, they establish a network connection, mount partitions from external SCSI hard drives, or carry out other hardware-specific actions. The scripts for the card manager are located in /etc/pcmcia. The scripts for hotplug can be found in /etc/hotplug.

If the card is removed, card manager or hotplug terminates all card activities using the same scripts. Finally, the modules that are no longer required are unloaded.

Both the start process of PCMCIA and card events are recorded in the system log (/var/log/messages). It records which PCMCIA system is currently used and which daemons have been used by which scripts to set up things. Removing a PCMCIA device should work smoothly, at least in theory. This works very well for network, modem, or ISDN cards as long as there are no active network connections. It does, however, fail if mounted partitions of an external hard drive or NFS directories are used. In such cases, ensure that these units are synchronized and cleanly unmounted. This is no longer possible if the card has already been removed. In case of doubt, cardctl eject can be helpful to safely eject the card.

This command deactivates all cards still in the laptop. To deactivate only one card, specify the slot number, for example, cardctl eject 0.

These can be set up with YaST like normal network cards. Select ‘PCMCIA’ as the card type. All other details about setting up the network can be found in Section 14.4. “Network Integration”. Read the notes there about hotpluggable cards.

Even for ISDN PC cards, configuration is done to a large extent using YaST, as with other ISDN cards. It is not important which PCMCIA card offered there is chosen, but only that it is a PCMCIA card. When setting up hardware and provider, make sure the operating mode is set to hotplug and not to onboot.

ISDN modems also exist for PCMCIA cards. These are modem cards or multifunction cards with an additional ISDN connection kit. They are treated like an ordinary modem.

For modem PC cards, there are normally no PCMCIA-specific settings. As soon as a modem is inserted, it is available under /dev/modem.

There are also “soft modems” for PCMCIA cards. As a rule, these are not supported. If there is a driver, it must be individually integrated into the system.

The corresponding driver module is loaded by the card manager or hotplug. When a SCSI or IDE card is inserted, the devices connected to it are available. The device names are detected dynamically. Information about existing SCSI or IDE devices can be found in /proc/scsi or /proc/ide.

External hard drives, CD-ROM drives, and similar devices must be switched on before the PCMCIA card is inserted into the slot. Use active termination for SCSI devices.

	Removing IDE or SCSI Cards
If you intend to remove a SCSI or IDE card, properly unmount all partions on these devices. Otherwise you would not be able to access these devices after a reboot of the system.

You can also install Linux entirely on external hard drives. However, the boot process is a bit more complicated. You will always need a boot disk containing the kernel and an initial ramdisk (initrd). More information about this can be found in Section 12.3. “Booting with the Initial Ramdisk”.

The initrd contains a virtual file system that includes all required PCMCIA modules and programs. The boot disk (or rather the boot disk image) is designed in a similar fashion. Using these, you could always boot your external installation. It is, however, tiresome to load the PCMCIA support every time by hand. Advanced Linux users can create a customized boot disk for their own system. For more information on this topic refer to the PCMCIA HOWTO, section Booting from a PCMCIA Device.

If the system hangs at boot time showing the message PCMCIA: Starting services or other strange things happen, PCMCIA can be prevented from being started at the next system boot by entering NOPCMCIA=yes at the boot prompt. To further isolate the error, load the three base modules of the PCMCIA system with the following commands by hand (as user root):

modprobe -t <dir> pcmcia_core
modprobe -t pcmcia-external i82365

for external PCMCIA or

modprobe -t pcmcia yenta_socket

for kernel PCMCIA

(in very rare cases, modprobe -t <dir> tcic)

and

modprobe -t <dir> ds

The critical modules are the first two.

If the error occurs while pcmcia_core is loaded, refer to the manual pages for pcmcia_core for further information. Use the options described there for a first testing with modprobe. As an example, switch off the APM support for the PCMCIA module. In a few cases, there could be problems with this. Use the setting do_apm=0 to deactivate power management:

modprobe -t <dir> pcmciacore do_apm=0

If the chosen option is successful, write it to the variable PCMCIA_CORE_OPTS in /etc/sysconfig/pcmcia to use it permanently:

PCMCIA_CORE_OPTS="do_apm=0"

Checking free I/O areas may lead to problems if other hardware components are disturbed by this. Avoid this by using probe_io=0.

If several options should be used, separate them by spaces:

PCMCIA_CORE_OPTS="do_apm=0 probe_io=0"

If errors occur while loading the i82365 module, refer to the manual page of i82365.

A problem in this context is a resource conflict — if an interrupt, I/O port, or memory area is occupied twice. Although the module i82365 checks these resources before they are made available to a card, sometimes just this check leads to problems. Checking the interrupt 12 (PS/2 devices) on some computers leads to the mouse or keyboard hanging. In this case, the parameter irq_list=<List of IRQs> can help. The list should contain all IRQs to use. For example, enter the command modprobe i82365 irq_list=5,7,9,10 or permanently add the list of IRQs to /etc/sysconfig/pcmcia:

PCMCIA_PCIC_OPTS="irq_list=5,7,9,10"

In addition, there are /etc/pcmcia/config and /etc/pcmcia/config.opts. These files are evaluated by card manager. The settings made in them are only relevant when loading the driver modules for the PCMCIA cards. In /etc/pcmcia/config.opts, IRQs, I/O ports, and memory areas can be included or excluded. The difference from the option irqlist is that the resources excluded in config.opts are not used for a PCMCIA card, but are still checked by the base module i82365.

Here, there are basically three variations: the card is not detected, the driver cannot be loaded, or the interface made available by the driver is set up incorrectly. Determine whether the card is managed by the card manager or hotplug. For external PCMCIA, card manager always takes control. For kernel PCMCIA, card manager manages PC card cards and hotplug manages CardBUS cards. Here, only the card manager is discussed.