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Re: [PATCH] PCI serial card support


From: n0ano
Subject: Re: [PATCH] PCI serial card support
Date: Sat, 8 Nov 2008 18:58:19 -0700
User-agent: Mutt/1.4.2.1i

I think this is pretty much what I'm in the middle of doing.  I want to
put the infrastructure in place so that we can handle an arbitrary PCI
device but I will only put the actual code in to handle the PCI card that
I have (the only one I can test).

What I'm doing is creating a table that matches the tuple (vendor id,
device id, subsystem vendor id, subsystem device id, device type, device
type mask) to a base baud and a configuration function.  The default
configuration function does nothing so the table only provides the base
baud.  We can add config functions for different cards as time goes by.

The user can always specify a specific I/O port and base baud for his/her
specific device, the table is really just a heuristic to provide a reasonable
default that can always be over-ridden.

Note that what I'm doing will make the serial module dependent upon the
pci module but I don't see that that's a big concern.  Pretty much any
modern machine will have a PCI bus so scanning it should not be a
problem.  Also, note that the legacy serial devices (I/O ports at
0x3f8 & 0x2f8) are going away, in the not too distant future the only
way to get serial output will be through PCI or USB.  Given that USB
controllers hang off the PCI bus I don't see an issue with having the
serial module require the pci module.

On Sat, Nov 08, 2008 at 01:45:44PM +0100, Robert Millan wrote:
> On Sat, Nov 08, 2008 at 02:23:32PM +0200, Vesa J????skel??inen wrote:
> > > 
> > > Why not use PCI ID to support this particular card?  This way Donald 
> > > doesn't
> > > have to support all cards, but the base is laid out so more cards can be 
> > > added
> > > in the future.
> > 
> > I have nothing against that. But in any case I think there has to be
> > this override functionality support. Just make it a bit harder for user
> > to type so they know it is advanced feature :).
> 
> How about implementing the flag but not listing it in --help output, and
> not documenting it (oh wait, we didn't document serial.mod anyway ;-)) ?
> 
> > Of course you can dynamically check if PCI module is there and
> > then ask identification information from there.
> 
> Sounds good.  But do we have support for "weak" symbol dependencies a la
> dlym() ?
> 
> -- 
> Robert Millan
> 
>   The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
>   how) you may access your data; but nobody's threatening your freedom: we
>   still allow you to remove your data and not access it at all."
> 
> 
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-- 
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
address@hidden
Ph: 303/443-3786




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