From: Paul Eggleton 
Subject: Linux on Toshiba laptops - DMA
Date: Sat, 1 Apr 2006 19:27:05 +1200

... I've recently 
set up my M50 and I thought you might like to know there is a way to enable 
DMA on the DVD drive. The issue is firstly the SATA driver needs to be told 
to handle the ATAPI DVD drive (which it doesn't by default), but also the 
IDE driver seems to grab hold of the DVD drive first, so that needs to be 
removed to get it to work. To accomplish this:
 1. Compile your own kernel (2.6.16 or later) with the following options:
  * Disable IDE options or make them modules
  * Set SCSI disk and SCSI generic as modules
  * Set Serial ATA and Intel PIIX/ICH support as modules

 2. Run "make modules_install" and also put the kernel image into /boot as 

 3. Edit /etc/mkinitrd/modules to have the following contents:

libata atapi_enabled=1

 4. Build the initrd:
mkinitrd -o /boot/initrd.img-version version
(if you get an error about mkext2fs you will need to 
edit /etc/mkinitrd/mkinitrd.conf and replace mkext2fs with mkcramfs).

 5. Run update-grub

 6. Reboot and all should be well :)