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Author Topic: More serial ports? Kernel parameter changes needed I think...  (Read 4319 times)

Offline the_beast666

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Hi all

I'm trying to get TC to run on an old pc/104 SBC I have lying around.  I intend to use it with ser2net so I can access a number of serial devices on my home automation system.  The specs are a little on the low side (166MHz pentium-class CPU, 128MB RAM with 4MB reserved for graphics, 32MB IDE flash storage) but after a lot of trial and error and a lot of learning I have microcore running with a static IP address.

But I've hit a problem - the SBC has 4 serial ports on board, and I have an ISA expansion card with another 4 ports on it - and I need at least 6 ports for my current devices.  The trouble is I can't get the add-in card to work.  I think that this is down to TC only supporting 4 ports in the kernel (but I'm new to the whole linux thing, so I may be wide of the mark with that!).

Is there any simple way of adjusting the kernel parameters to allow my system to use 8 ports?  I've tried adding:

CONFIG_SERIAL_8250_NR_UARTS=8
SERIAL_8250_RUNTIME_UARTS=8

to the extlinux.conf file, but they appear to be ignored (and I'm not even sure if they're relevant to be honest!).  Do I need to recompile the kernel from scratch?  I'm not sure either my brain nor my little CPU could cope with that...


Offline Misalf

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Re: More serial ports? Kernel parameter changes needed I think...
« Reply #1 on: March 07, 2016, 05:00:54 AM »
Hi,
maybe this helps?
https://www.kernel.org/doc/Documentation/kernel-parameters.txt

Quote
nr_uarts=   [SERIAL] maximum number of UARTs to be registered.
Download a copy and keep it handy: Core book ;)

Offline Misalf

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Re: More serial ports? Kernel parameter changes needed I think...
« Reply #2 on: March 07, 2016, 05:05:51 AM »
The kernel in 7.x x86 was compiled with
Code: [Select]
CONFIG_SERIAL_8250_NR_UARTS=32
CONFIG_SERIAL_8250_RUNTIME_UARTS=4
Download a copy and keep it handy: Core book ;)

Offline gerald_clark

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Re: More serial ports? Kernel parameter changes needed I think...
« Reply #3 on: March 07, 2016, 06:17:04 AM »
 Try "8250.nr_uarts=8" in extlinux.conf.

Offline the_beast666

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Re: More serial ports? Kernel parameter changes needed I think...
« Reply #4 on: March 07, 2016, 07:29:11 AM »
thanks everyone - with the "8250.nr_uarts=8" added in I got the additional ports to show up.  I then encountered an issue with setserial failing with an "invalid argument" error, but that's also sorted now (I needed to set the base baud rate before I could set the other port parameters in case anyone else has this problem).

Now I just need to try and get it to actually do something useful  :)