linux-kernel - Re: [PATCH] - Increase PNP_MAX_PORT. ACPI devices can have a lot IO resource declarations

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Message-Id: <200707181533.25366.bjorn.helgaas@hp.com>
Date:	Wed, 18 Jul 2007 15:33:25 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	trenn@...e.de
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Alexey Starikovskiy <aystarik@...il.com>,
	Jean Delvare <khali@...ux-fr.org>,
	Bernhard Walle <bwalle@...e.de>
Subject: Re: [PATCH] - Increase PNP_MAX_PORT. ACPI devices can have a lot IO resource declarations

On Wednesday 18 July 2007 02:21:14 am Thomas Renninger wrote:
> On Tue, 2007-07-17 at 09:49 -0600, Bjorn Helgaas wrote:
> > On Monday 16 July 2007 08:21:07 am Thomas Renninger wrote:
> > > PNP0C02 devices normally have a lot more IO port declarations than
> > > currently defined in PNP_MAX_PORT
> > 
> > Yes.
> > 
> > > I also wonder whether other limits like:
> > >  #define PNP_MAX_MEM        4
> > >  #define PNP_MAX_IRQ        2
> > >  #define PNP_MAX_DMA        2
> > > could get exceeded with pnpacpi?
> > 
> > Definitely.  I think the current limits come from the PNP ISA spec
> > (sec 4.6).  I don't see similar limits in the PNPBIOS or ACPI specs,
> > so ideally I think they should be dynamically allocated as you suggest.
> > 
> I wanted to implement the dynamic approach and used a dynamically
> allocated array, filled up from beginning. While this is close to the
> current implementation I thought this is the easiest sufficient way...
> (I also only did this for io ports where most mem is wasted).
> Now I am thinking about hotplug (e.g. if a SSDT with resources gets
> hot-added, removed)... If a device can vanish, the array must get
> reordered, not a really well fitting structure, a list (a pnp specific
> set up, or from include/linux/list.h?) should be better?

I don't understand the array reordering problem.  Either a device exists
or it doesn't.  Loading or unloading an SSDT should not change the number
of resources for devices (except that it might add or remove an entire
device).

I think for now, it would be sufficient to increase PNP_MAX_IRQ to 8
and PNP_MAX_PORT to 32 and be done with it.  I don't think it's worth
getting more complicated unless we dynamically allocate everything.

Bjorn
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