On Tue, 13 Jun 2023 19:29:19 +0200, Mark Brown wrote: > > On Tue, Jun 13, 2023 at 07:05:21PM +0200, Takashi Iwai wrote: > > Mark Brown wrote: > > > > > Oh, I'm afraid that we're seeing different things. The code there is > > > > rather to *set* some initial value for each amp register (but only > > > > once), and it's not about optimization for writing a same value > > > > again. > > > > > That is, the function helps to set an initial (mute) value on each amp > > > > when the driver parses the topology and finds an amp. But if the > > > > driver already has parsed this amp beforehand by other paths, it skips > > > > the initialization, as the other path may have already unmuted the > > > > amp. > > > > So it is possible that we might set two distinct values during setup > > > then and we're doing this intentionally? It's not obvious that this > > > might happen. A comment wouldn't hurt, and a big part of this is > > > confusing is that in the non-regmap case all we're doing is suppressing > > > duplicate writes, in that path it's just checking for changes in the > > > register value. > > > > None of this is what the non-regmap path does, it just suppresses noop > > > writes to the hardware. > > > Actually, many of HD-audio codec driver code heavily relies on the > > regmap, more or less mandatory. The snd_hda_codec_amp_init() is one > > of such. You may write a codec driver without the regmap, but some > > helpers won't work as expected. > > Sounds like it might be so thinly used it's becoming mandatory to have a > regmap in order to avoid gotchas like there might be with things getting > muted? It's rather historical reasons. The caching mechanism was already present and mandatory from the beginning, but it was implemented in a different way. Later on, it was translated to the regmap. Meanwhile, we generalized the HD-audio codec driver to be on a generic HD-audio bus, and this allowed the use without regmap. So some basic helpers are designed to work without regmap but some are still tightly tied with regmap. Takashi
