Once Again;
Thankyou very much Clemens!
johnu
-----Original Message-----
From: Clemens Ladisch [mailto:cladisch@xxxxxxxxxxxx]
Sent: Thu 3/1/2007 12:25 AM
To: John Utz; alsa-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: what criteria should be used to choose between snd_ac97_update_bits, snd_ac97_write, snd_ac97_write_cache ?
John Utz wrote:
> are there reasons why one might prefer one of these or the other?
Because reading AC'97 registers is rather slow, there is a cache of
register values.
Use snd_ac97_write() for registers that should not be cached.
Use snd_ac97_write_cache() to write to a register that can be cached,
i.e., later reads can take the value from the cache instead of reading
from the codec.
Use snd_ac97_update() to write to a register where writing the same
value would not have any effect.
Use snd_ac97_update_bits() in the same situation as snd_ac97_update(),
but when you want to update only some bits.
Use snd_ac97_read() for uncached reads; and snd_ac97_read_cache() for
reads from the cache, if possible.
HTH
Clemens
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