[alsa-devel] [PATCH] opti931: additional check for OPL3 device

[Clemens Ladisch]

Krzysztof Helt wrote:
> "Clemens Ladisch" <cladisch at fastmail.net> wrote:
> > Krzysztof Helt wrote:
> > > This patch adds additional check for OPL3 device. I found that PNP
> > > region returned by the card is 0x380 - 0x38f but the OPL3 device is
> > > located at 0x388 (standard FM device address).
> > 
> > On cards with an OPL4, it would use the entire range, where that last
> > eight bytes are the OPL3-compatible registers.
> 
> Ok. I haven't touched the size of the range or the range itself. I just added
> a fallback to check range +8 (which is 0x388) after failure to find the OPL3
> at the 0x380.
> 
> > My card doesn't have PnP, but I guess the OPL4 detection wouldn't work
> > on 92x either for the same reason.
> 
> Should the OPL4 detection has the same fallback or just all Opti cards
> should search the FM chip at the range + 8 address?

It appears a fallback shoudn't be needed because the chip always returns
a range suitable for an OPL4.

Since an OPL3 range is never larger than 8 bytes, and OPL4 needs 16
bytes, we could add 8 to get the FM address _if_ the range is at least
16 bytes; thus we are safe even if a chip publishes an OPL3-only range.


Regards,
Clemens