Disable hardware polling for CD-drives

hal cdrom polling hal is a core component of the various desktop environments and deals with all sorts of hardware interaction. One component of the hal daemon is the part where it polls the cdrom drive regularly (as often as once every two seconds!) to see if the user has inserted a CD. This is used, for example, to automatically open a new window with a file browser for the CD.

Such regular polling will keep the hardware awake somewhat; the amount of power consumed depends on the exact type of CDROM drive. It also depends on the presence of the ALPM feature.

If you rarely or never insert CDs (for example because the machine in question is a server located 3000 miles away), you can save some power by stopping this polling.

Current versions of hal have a special command for this:

hal-disable-polling --device /dev/scd0

Note that this means that you will not get a pop-up window if you insert a CD. To enable this polling again, use the this command:

hal-disable-polling --device /dev/scd0 --enable-polling

Newer SATA-based CDROM drives have the capability to notify the machine when a CD gets inserted, making polling unnecessary. Both the kernel and hal are currently undergoing development to detect and support this capability, so that polling is not needed at any time for these devices.