Re: what criteria should be used to choose between snd_ac97_update_bits, snd_ac97_write, snd_ac97_write_cache ?

["Clemens Ladisch" <cladisch@fastmail.net>]

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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