15 May
2021
15 May
'21
8:26 p.m.
On Sat, May 15, 2021 at 7:24 AM Fons Adriaensen <fons(a)linuxaudio.org> wrote:
On Sat, May 15, 2021 at 06:49:28AM -0600, Paul Davis
wrote:
That's what was changing in the late 1990s. Before "DMA-capable" audio
interfaces, you needed special data transfer operations to get data to/from
the audio interface. By 2000-2002, that mostly went away, and they were all
DMA capable. ALSA evolved to accommodate this, but there had been no reason
to focus on mmap-style access before then.
Also, at that time, ALSA didn't yet properly
support the mmap'ed mode ...
it was under development but not finished (as evidenced by the way it
could
not handle non-interleaved devices like the RME
digi series.
That's another thing that puzzles me...
At the time audio cards like the RMEs would be sitting on a PCI bus,
and the mmap area could/would be actual hardware buffers.
So then, mmapped mode would be the 'natural' way, with read()/write()
being implemented on top of it. But apparently it was the other way
around...