Re: CD writing in future Linux (stirring up a hornets' nest) (was: Rationale for RLIMIT_MEMLOCK?)

[Jens Axboe <axboe@suse.de>]

On Wed, Jan 25 2006, Jens Axboe wrote:
> On Wed, Jan 25 2006, Jan Engelhardt wrote:
> > 
> > >> And if you check the amount of completely unneeded code Linux currently has 
> > >> just to implement e.g. SG_IO in /dev/hd*, it could even _save_ space in the 
> > >> kernel when converting to a clean SCSI based design.
> > >
> > >Please point me at that huge amount of code. Hint: there is none.
> > 
> > I'm getting a grin:
> > 
> > 15:46 takeshi:../drivers/ide > find . -type f -print0 | xargs -0 grep SG_IO
> > (no results)
> > 
> > Looks like it's already non-redundant :)
> 
> SG_IO turns requests into REQ_BLOCK_PC (or blk_pc_request()) types, so
> you should probably check for that as well. But it's truly a miniscule
> amount of code, and if I got off my ass and folded cdrom_newpc_intr()
> and cdrom_pc_intr() into one (that was the intention), it would be even
> less.

BTW, I should point out that the fact that references to REQ_BLOCK_PC
and blk_pc_request() exists doesn't indicate duplicated code. Each low
level driver or layer (like SCSI, not the SCSI low level drivers) need
to transform REQ_BLOCK_PC requests into their command types.

-- 
Jens Axboe

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