[alsa-devel] getting dynamic state from ac97 bus ops

[Mike Frysinger]

On Mon, Mar 28, 2011 at 06:06, Mark Brown wrote:
> On Sun, Mar 27, 2011 at 10:48:52PM -0400, Mike Frysinger wrote:
>> is there an obvious way that i'm missing to get at the bus state from
>> the funcs in the global soc_ac97_ops structure ?  the ac97 bus drivers
>> that i see in the tree simply have a global variable for state and
>> that sort of defeats the purpose of having multi-instance support in
>> the first place ...
>
> I'm not sure what you mean by "bus state" but the AC'97 support in ASoC
> is really intended for the sort of single CODEC systems you typically
> see on embedded boards.  It's mostly there because some of the later
> AC'97 CODECs started to grow a lot of non-standard power management and
> routing.

looking at the cpu dai drivers which declare soc_ac97_ops:
au1x/psc-ac97.c:au1xpsc_ac97_workdata
ep93xx/ep93xx-ac97.c:ep93xx_ac97_info
fsl/mpc5200_psc_ac97.c:psc_dma
... and so on ...

this is state specific to the ac97 bus connection (snd_ac97_bus_ops),
not the specific machine driver which links the codec to the
transport, and currently all of these guys do it globally.  which
means only 1 AC97 codec can be in play in the system.

the Blackfin has multiple SPORTs and could do one AC97 codec per
SPORT.  but atm, there is only one global soc_ac97_ops structure, and
i cant see how the functions in that structure could get at the
link-specific state so that the bus driver would work with multiple
AC97 codecs.

granted, no customer that i know of has asked for this (more than AC97
codec), it's just a limitation i noticed when working on an AC97
driver, and i figured i might as well do it right while i'm cleaning
crap out already.

so atm i have:
...
static struct sport_device *ac97_sport_handle;
...
static unsigned short bf5xx_ac97_read(struct snd_ac97 *ac97,
    unsigned short reg)
{
    struct sport_device *sport_handle = ac97_sport_handle;
...

when really i'd expect ac97_sport_handle to not exist and to be able
to get that via the struct snd_ac97 that gets passed in.
-mike