Re: Christmas list for the kernel

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Wed, Nov 23, 2005 at 04:39:35PM +0100, Pierre Ossman wrote:
> Russell King wrote:
> >On Wed, Nov 23, 2005 at 04:20:00PM +0100, Pierre Ossman wrote:
> >  
> >>But if no hardware is connected to those devices, then where does the 
> >>driver route the setserial stuff?
> >>    
> >
> >setserial /dev/ttyS2 port 0x200 irq 5 autoconfig
> >
> >and you might then end up with another serial port detected.  If
> >/dev/ttyS2 and above do not exist, you can't do that.  That would
> >in turn effectively prevent folk with some serial cards using them
> >with Linux without editing and rebuilding their kernel.
> 
> Ah. But why is this not done through module parameters? That would be 
> more consistent with how you specify resources for other drivers.

Take a moment to consider how you would supply a large number of ports
via this method - eg, 16 ports, where a port IO and IRQ configuration
takes about 10 characters ("0x1234,11"), and then what about the baud
base, probe flags (auto_irq, skip_test) ?

Also consider that ttyS0 might be your serial console for your headless
box, so you're unable to build 8250 as a module in the first place.

It really isn't simple.  Serial _is_ special - and that is why it keeps
sprouting new and wonderful initialisation paths.  I'd rather not add
yet another gods greatest invention initialisation path on top of those
we already have.

> >As for the rest of the "setserial stuff" it gets recorded against
> >the port and remembered for when the hardware turns up, which it
> >may do if it's your PCMCIA modem card.
> 
> This could be a bit more questionable. Setting the initial state of 
> hardware is better done (IMHO) by reacting to some hotplug event. E.g. 
> fedora uses an 'install' line in modprobe.conf to restore mixer state 
> for sound cards.

Actually, my example was slightly flawed - when the hardware turns up
it gets reset back to something sane.  So the settings are merely
remembered while the hardware doesn't exist.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core