At Wed, 03 Dec 2003 20:00:05 +0100,Please elaborate here: does that mean that if I have 3 soundcards (eg. 3 emu10k1 cards) and 6 snd-serialmidi devices
Benno Senoner wrote:
Hi, (I'm using alsa-driver-1.0.0rc1)
I have a question about the SNDRV_CARDS. normally it is defined as 8 ./alsa-kernel/core/memalloc.c: #define SNDRV_CARDS 8
Does that mean we can have a maximum of 8 soundcards
in the PC or is this simply how many instances a certain module supports ?
(eg I could have 8 emu10k instances, 8 sb16 instances etc ?).
no, totally 8 instances. not the number of modules.
( = total of 9 "cards"), that this configuration does not work ?
Then I see no reason not to fix it, or at least place a big FIXME in the sources near thePlus I noticed something in
./alsa-kernel/core/memalloc.c: static int enable[8] = {[0 ... (SNDRV_CARDS-1)] = 1};
shouldn't that be:
static int enable[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS-1)] = 1}; ?
yes, but not a bug as long as SNDRV_CARDS = 8 :)
SNDDRV_CARDS definition.
Otherwise when these SNDRV_CARDS limits will be lifted someday developes
will need to fix these nasty fixed array size assumption.
I did look at /dev/snd:
is this a bug ? what happens if we set SNDRV_CARDS to a value > 8 ?
more than 8 cards are not supported in the current assignment of devices. the minor devices will be out of range.
devicename, maj, min
/dev/snd/midiC0D0 116, 8 /dev/snd/midiC0D1 116, 9
....
/dev/snd/midiC0D7 116,15
/dev/snd/pcmC0D0p 116, 16 /dev/snd/pcmC0D1c 116,25 /dev/snd/pcmC0D1p 116,17 /dev/snd/pcmC0D2c 116,26 ...
Is that the minor devices conflict you are refering to ?
I assume the midi serial devices allocate a /dev/snd/midiC0Dx device thus only 8 midi ports
per card are allowed.
After midiC0D7 (116,15) comes pcmC0D0p (116, 16) so there would be no room for
midiC0D8, right ?
The question is now: is it possible to change the device major,minor number layout to allow
for more /dev/snd/midiCxDy devices (and simultaneously increasing SNDRV_CARDS) ?
Is it simply a matter of changing the snddevices script or does alsa-driver/alsa-lib make assumptions
about the devicenode numbers thus rendering such modifications useless ?
About the minor number:
I understand it is limited to 1 byte thus has a 0-255 range.
I did look at the snddevices script and it seems that every card uses 32 minor numbers thus
32 * 8 cards = 256 = full range used.
Even if the script only creates the device nodes for the first 4 cards (thus minor numbers 0-127) I assume
you can redefine MAX_CARDS in the script and create the device nodes for all 8 cards.
in ./alsa-kernel/include/minors.h I see:
#define SNDRV_MINOR_DEVICES 32 #define SNDRV_MINOR_CARD(minor) ((minor) >> 5) #define SNDRV_MINOR_RAWMIDI 8 /* 8 - 15 */ #define SNDRV_MINOR_RAWMIDIS 8 #define SNDRV_MINOR_PCM_PLAYBACK 16 /* 16 - 23 */ #define SNDRV_MINOR_PCM_CAPTURE 24 /* 24 - 31 */ #define SNDRV_MINOR_PCMS 8
So basically as far as I understand those macros would need to to be changed too.
I see PCM_PLAYBACK and PCM_CAPTURE each taking up 8 device nodes each.
Perhaps I could reduce that to 4 thus making room for 2*4=8 more RAWMIDI devices ?
(but these are per card so I guess that is the wrong way to go, read below)
The question how many multiple PCM_PLAYBACK devices are usually needed ?
Of course this depends from the card. For example for my CMI8738MC6 card
in /proc/asound I see: pcm0c, pcm0p, pcm1p, pcm2c, pcm2p
thus 3 devices each for playback and capture.
What happens in the case of the hammerfall where you can have up to 24 playback channels ?
Is that seen as a single capture/playback device ? Or cards like the delta 1010 ?
Ok the good old Steve Harris just did a cat /proc/asound/ on his Hammerfall box for me:
id, oss_mixer, pcm0c, pcm0p, rme9652
So it means it uses only one pcm device.
But the big doubt is: since Takashi said each snd_serialmidi device allocates one of the available
SNDRV_CARDS slots it basically means that we use only one midiCxDy per card.
If I use the module options line Takashi gave me
options snd-serialmidi enable=1,1,1,1 sdev=/dev/ttyS2,/dev/ttyS3,/dev/ttyS4,/dev/ttyS5
and I do aconnect I get something like
72:0 Serial Midi Device 1 (or was the name Raw Midi ? does not matter for explanation purposes).
80:0 Serial Midi Device 2
88:0 ....
So I assume of each "card" only /dev/snd/midiCxD0 is used.
Correct me if I'm wrong.
To make it short, do you think I have a chance to succeed increase SNDRV_CARDS to 12-16
(and change the snddevices script and the SNDRV_ macros) ?
Must each card use a power of two (currently 32) of minor device nodes ?
If that is true then the only alternative would be SNDRV_CARDS = 16 but that would leave only
16 minor numbers for card which is too little to make fit a few pcm devices, rawmidi and the other stuff neded.
Perhaps the ideal tradeoff would be SNDRV_CARDS=12 but that would require a per card
minor device number that is not a power of two.
Ok some macros would become a bit slower eg (assuming 20 minor ids per card)
#define SNDRV_MINOR_CARD(minor) ((minor) / 20)
But this is not the end of the world.
Let me know please. I'll share my experiences (problems, failures, success etc) here on the mailing list.
thanks, Benno http://www.linuxsampler.org
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