Re: New Mitsumi legacy CD-ROM driver

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On 05/08/2007 12:35 PM, Jens Axboe wrote:

Thanks very much for the prompt answer!

bio[n - 1].bi_sector + bio_sectors(bio[n - 1]) == bio[n].bi_sector

IOW, the bio's in the chain on the request are contig in the lba space.

Okay great, thanks, everything fine then.

Yeah, I think it's pointless to support highmem. And as long as you
don't call blk_queue_bounce_limit() to actively enable highmem, you are
not going to receive a bio/request with highmem pages.

Yep, the driver is setting BLK_BOUNCE_ANY.

The block layer wil bounce any highmem pages before it reaches you. So
for a driver like this, I would recommend just forgetting the mapping
aspect.

Okay, I agree highmem doesn't make any practical sense for this driver but I'm not really sure what it would gain. if !CONFIG_HIGHMEM the bvec_kmap_irq turns info "(page_address((bvec)->bv_page) + (bvec)->bv_offset)" directly anyway. I am a bit unsure about it all but it's not the case that we can then leave out the entire bio_for_each_segnment() loop is it?

(generic kernels with HIGHMEM enabled are I guess an argument...)

I don't have time to review your driver right now, but I will applaud
your effort to write a maintenable mitsumi driver! Basically all the old
cdrom drivers are utter crap, so they are destined for removal.

I noticed by the way there was a bit too much emphasis on the "I" in this message; it's in fact Pekka Enberg who started this and did the core stuff!

Yes ,the current legacy CD-ROM drivers really are complete crap by now. Once this mitsumi driver is in final shape it should serve as a nice template for the few other types that I'd like to keep supported and the rest can just go.

Thanks again for the prompt comments.

Rene.

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