[asterisk-dev] /dev/zap/(channel no) ends on 255 and unable tomake more

[Paul Cadach]

Hi,

/dev/zap/<channel no> used mostly for non-specific tools (like dd 
if=/dev/zap/1 of=/tmp/chan1_mon.alaw ;-) ). Real channel drivers and 
zaptel-specific tools should use /dev/zap/channel interface instead. You can 
easily update chan_ss7 to use /dev/zap/channel mechanism (just look how it 
is implemented in chan_zap already - it is additional ioctl() call to bind 
the descriptor to specific Zaptel channel).

As for DEVFS, it's not plays any role. Most limitation is by design of /dev/ 
filesystem in *nix-systems which uses one-byte major and minor numbers to 
identify device node. Zaptel uses its own major number, so it have limited 
to 256 only minor device numbers, and few of them are reserved for specific 
devices (like /dev/zap/channel, /dev/zap/timer, /dev/zap/pseudo).


WBR,
Paul.

----- Original Message ----- 
From: "Anton VG" <anton.vazir at gmail.com>
To: "Asterisk Developers Mailing List" <asterisk-dev at lists.digium.com>
Sent: Friday, December 22, 2006 11:49 AM
Subject: Re: [asterisk-dev] /dev/zap/(channel no) ends on 255 and unable 
tomake more


> in fact chan_ss7 uses this method to access a channel which
> provides the signalling link. And if I use that on the
> span>8 ... so than I can't use chan_ss7. Matthew, looking
> for a time when you'll sync your libss7 with 1.4 ;) Until
> now have to stick with chan_ss7. Not sure, but is this a
> limitation of DEVFS?
>
> 2006/12/23, Matthew Fredrickson <creslin at digium.com>:
>>
>> On Dec 22, 2006, at 11:49 AM, Anton wrote:
>>
>> > Guys,
>> >
>> > In a system with more than 8xE1 it's impossible to access
>> > to /dev/zap/(channel no) channels higher than 255. ZAPTEL
>> > Makefile generates only 255 instances and adjusting
>> > Makefile to be generating more of them, makes any nodes
>> > over 255 to be anyway dead (attempt to access returns (for
>> > instance 256's node) "Cannot open "256" No such device or
>> > address (6)" error. If someone could please give a clue how
>> > to make them accessible, it will be highly appreciated. Is
>> > it a linux limitation or just a variable in Zaptel sources?
>> > Please help.
>>
>> What do you need this for?  If this is for asterisk, then you don't
>> have anything to worry about.  A very cursory overlook of chan_zap
>> shows that it does not open the zap devices by those means.  There is
>> another mechanism for opening zap channels provided through
>> /dev/zap/channel that gets around the limitation with devices nodes.
>>
>> Matthew Fredrickson
>>
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