Messages in this thread | | | From | Benjamin Herrenschmidt <> | Subject | Re: [PATCH] IDE 58 | Date | Wed, 8 May 2002 21:49:31 +0200 |
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> >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.
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