Do we still need ATA disk CHS addressing?

Alexander Motin mav at
Mon Aug 10 19:59:27 UTC 2009

Warner Losh wrote:
> My question, and maybe I missed this earlier in the thread, is what's
> the benefit to removing this support?  How much code is saved?

It is not about code size, but about code structurization. ATA(4) has 
too much cross-level relations, making it cryptic. I am trying to unroll 
some of them to simplify code.

> Having said all that, I think it is OK, but I'd definitely poll the
> pc98 guys first...  Just to make sure they don't need it and re-fork
> the ata driver to get it :)

GEOM has no terms of cylinders/heads/sectors, in fact it works only with 
LBA. CHS translation is only needed for drives, that have no native LBA 
support. It is not about disk partitioning or label format. It is just a 
method to linearize nonlinear address space of ancient drives. For last 
10 years, since drives lost their classic geometry, drives are doing 
this translation on firmware level.

Alexander Motin

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