Re: Fixing Wireless PC Card 16550A UART Serial Device Assignment

["Michael G. Morey" <mmorey@optivel.com>]

Luke Anderson wrote:

> On Friday 30 July 2004 19:56, Michael G. Morey wrote:
>  
>
> > All,
> >
> > I'm running Debian GNU/Linux 3.0r1 with hotplug, modutils, pciutils, and
> > usbutils back-ports from www.backports.org, on a Dell Latitude D800
> > laptop.  I'm running a custom Linux 2.4.26 kernel I've built from a
> > Debianized back-port, configured for 16550A UART support for PC card
> > devices.  I have a wireless modem PC card device, which maps alternately
> > to /dev/ttyS01 and /dev/ttyS02, seemingly at random.  I have a total of
> > three serial UART devices, and would like to have devices assigned
> > accordingly:
> >
> > /dev/ttyS0:  built-in serial port
> > /dev/ttyS1:  Conexant HSF Softmodem with Linuxant driver
> > /dev/ttyS2:  Sony Ericsson EDGE PC Card GC82 wireless modem
> >
> > On a good boot, the devices are assigned as follows:
> >
> > ttyS00 at 0x03f8 (irq = 4) is a 16550A
> > ttySHSF0 at I/O 0xb400 (irq = 11) is a Conexant HSF softmodem
> > ttyS02 at port 0x03e8 (irq = 3) is a 16550A
> >
> > However, occasionally, the devices are assigned as follows:
> >
> > ttyS00 at 0x03f8 (irq = 4) is a 16550A
> > ttySHSF0 at I/O 0xb400 (irq = 11) is a Conexant HSF softmodem
> > ttyS01 at port 0x03e8 (irq = 3) is a 16550A
> >
> > My dmesg output is attached.  I apologize if the attachment is not
> > accessible to some.
> >
> > Does anyone know of a way that I fix the PC Card serial device
> > assignment permanently, to /dev/ttyS02?
> >
> > In general, could anyone offer suggestions as how to fine-tune the
> > loading of device driver modules using the hotplug and/or modutils
> > packages?  When is hotplug appropriate, and when is it not?  Which
> > modules should be pre-loaded through /etc/modules?
> >    
> I think you may have hit the nail on the head there, /etc/modules should be 
> used for devices that you are going to use all the time, whereas hotplug is 
> for things that aren't connected all the time.
>
> The best solution would be to load the modules in /etc/modules.conf of the 
> respective devices, in the order you want them used.
>
> Seeing as you don't have enough devices and you want to use ttyS02, perhaps a 
> link in dev would suffice?
>
> cd /dev
> rm ttyS02
> ln ttyS01 ttyS02
>
> Will cause ttyS01 and ttyS02 to refer to the same physical device.
> This should sort out your problem.
>
>
>
>  
>
> > Please advise me if I'm omitting any pertinent details regarding my
> > configuration.
> >
> > Thanks in advance.
> >
> > Michael
> >    
>
>
>  
Actually, it's not the device file assignment which is the problem.  
It's the set of resources the device uses.  The kernel reports the 
device at /dev/ttyS01 or ttyS02.  The actual devices are /dev/ttyS1 or 
/dev/ttyS2.  Regardless of the device file name, the IRQ and/or I/O 
memory ranges are different.  My frustration lies in my ability to 
predict which IRQ and/or I/O memory range the device will be assigned at 
boot time.  I'd like very much to fix these parameters, but do not know 
how to do so, since it seems to be under the control of the hotplug 
subsystem, which has its own idea of how to allocate device resources.

Michael

--
Michael Morey
Consultant
Optivel
Phone: 317.275.2306
E-mail: mmorey@optivel.com
Web: www.optivel.com