Finally I figured out how to enable the rear channel separately from the front
on the creative labs CT5880 (= modified ens1371 as it seems).
I'll describe the settings to enable this, but I'm not going to submit a
patch, as I have noticed that I messed up my ens1370.c too much, and I can't
get a clean version because CVS doesn't work. It's a minor change, so I
assume it can be done by the maintainers.
The whole thing is in three bits in the BASE+0x04 register (ES_REG_STATUS in
the driver). These bits are bit27, bit26 and bit24
There are three modes of operation:
1) No rear output: bit27=bit26=bit24=0
2) rear output is a mirror of the main output, but controlled by the
'surround' slider of the mixer. I assume the ens1371 mixes the two 'devices'
and sends the mix to both MAIN and SURROUND DAC. This mode is selected by
setting bit27=bit24=0 and bit26=1
3) independant rear (surround) and front output. Using the current driver,
this has the strange side-effect that HW:0,0 becomes the rear output and
HW:0,1 becomes the front. So HW:0,0 is controlled by the 'surround' mixer
control, and HW:1,0 is controlled by the PCM and Master mixer controls. To
select this mode set bit27=bit24=1 and bit26=0. It seems that bit27=1 and
bit24=bit26=0 is identical, but the windows driver clearly does the first, so
why not? It works...
front only, no rear: bit27=0 bit26=0 bit24=0
rear mirrors front: bit27=0 bit26=1 bit24=0
front & rear independant: bit27=1 bit26=0 bit24=1 (x?)
I patched my driver by inserting the following code around line 1947:
(I included two lines of overlap to make the location easier to find)
=============================================
outb(ensoniq->uartc = 0x00, ES_REG(ensoniq, UART_CONTROL));
outb(0x00, ES_REG(ensoniq, UART_RES));
#ifdef CHIP1371
/* enable the rear outputs
This seems to work
ensoniq->cssr |= (0 << 27) | (1 << 24);
but the windows driver does this, so let's
also do it */
ensoniq->cssr |= (1 << 27) | (1 << 24);
/*
Use this for mirror mode
ensoniq->cssr |= (1 << 26);*/
#endif
outl(ensoniq->cssr, ES_REG(ensoniq, STATUS));
#if defined(CONFIG_GAMEPORT) || defined(CONFIG_GAMEPORT_MODULE)
=============================================
Maybe there is a better place to put this? I don't know... I put it in the
snd_ensoniq_create() function because I always want 4ch output, and I don't
see the use of the other modes in an ALSA enviroment.
Regards,
Pieter
PS: I'm also developing a driver for my Maxisound ISIS, where do I look for
information on ALSA/linux driver developement? Does anyone have a 'template'
ALSA driver?
Does ALSA support non-DMA audio transfer? I believe the ISIS uses this kind of
transfers, but I don't know for sure yet. I know it's stupid design not to
use DMA, but there is nothing to do about it I guess.
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