Comment 70 for bug 228302

Montblanc. I'm not sure of what kind of 'full speed writting' you are talking about.

My observation is that pata_ali DOES NOT WORK properly with CD/DVD drives. Burinig a disck using pata_ali is hardly possible, takes 100% cpu and takes forever since cdrom DMA transfers are disabled. Enabling DMA through /sys makes reading/writting impossible (errors).

Using ata_generic instead of pata_ali solves all the problems. DMA works fine. Current ubuntu kernels prevent the user to choose ata_generic over pata_ali!

Regarding possible inferior performance of ata_generic I've discovered that there are none. See attached performance and dmesg results.

Files: *.custom hold results for my customized kernel (see post #58) with ata_generic instead of pata_ali driver. Other files hold results for the current Karmic kernel with pata_ali.

So there are two possible solutions:
1. somebody fixes pata_ali driver which seems to be broken - mind the warning: WARNING: ATAPI DMA disabled for reliablity issues - it's ridiculous, especially that ata_generic works fine.
2. ubuntu developers prepare the kernel in such a way which allows to use generic_ata driver! which I agree is kind of workaround, but it might be just good enough, and it's way better that the current situation which prevents using a cdrom/dvd drive!