Linus Torvalds wrote:
The old situation with SATA drivers that had
if (iomem)
writel(..)
else
outl(..)
in the cases that needed it (and used hardcoded writel/outl in the cases
that didn't) was an example of code that "in theory" is faster. But
dammit, in practice that mattered not one whit, and what iomap() tries to
do is to attack the _real_ problem we had in that area.
Which had nothing what-so-ever to do with any branches.
And none of those issues are a factor at all in ath5k (which spawned
this sub-discussion), or indeed many other drivers. The above code you
cite is -generic-, hardware agnostic code.
Most new hardware is MMIO-only, making ioread32() only for drivers that
care about legacy IO support, something that is being slowly phased out.
e.g. legacy IDE, legacy 10/100 mbps ethernet NICs with the dual
MMIO/PIO register spaces.
Jeff
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