Re: [PATCH] IDE 58

[Benjamin Herrenschmidt]

>
>Please push it higher level than that. Load the taskfile as a set in
>each method. Remember its 1 potentially paired instruction to do an MMIO
>write, its a whole mess of synchronziation and stalls to do a function 
>pointer.

I though about that, but what about corner cases where only a single
register can be accessed ? (typically alt status). Provide specific
routines ? Also, how does the extended addressing works ? by writing
several times to the cyl registers ? That would have to be dealt with
as well in each host driver then.

>> address at all (that is kill the array of port addresses) but
>> just pass the taskfile_in/out functions the register number
>> (cyl_hi, cyl_lo, select, ....) as a nice symbolic constant,
>> and let the channel specific implementation figure it out.
>
>Pass  dev->taskfile_load() a struct at least for the common paths. Make the
>PIO block transfers also single callbacks for each block not word.

Right. We could go the darwin (apple) way and have taskfile_load/store
functions doing the entire registers controlled by a bitmask of which
registers has to be touched. it has a cost (testing each bit and
conditionally branching, which can suck hard) but probably less than
an indirect function call which isn't predictable.

Ben.