linux-kernel - Re: How should I handle device with two PNP-BIOS ids?

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Date:	Wed, 4 Feb 2009 17:00:19 -0700
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Ville Syrjälä <syrjala@....fi>
Cc:	Krzysztof Helt <krzysztof.h1@...pl>, Adam Belay <abelay@....edu>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: How should I handle device with two PNP-BIOS ids?

On Tuesday 27 January 2009 10:17:52 am Ville Syrjälä wrote:
> On Tue, Jan 27, 2009 at 08:52:51AM -0700, Bjorn Helgaas wrote:
> > Oh.  That sounds like a BIOS bug.  If there's only one actual
> > chip, the BIOS should not report it as two separate devices.
> 
> It's not a bug. The cs423x chips contain several logical devices.
> WSS, MPU401, joystick etc.

Sorry it took me so long to get back to this.

Yes, you're right.  I was thinking the first device had a set of
resources, and the second device had a superset that included the
same resources plus another one, but that's not the case here.

> The control logical device (which is 
> not present in the early models) is unfortunately some kind of dumping
> ground for new registers to keep the other logical devices' backwards
> compatible. It contains at least some extra mixer control registers and
> power management registers.

In this case, you have:

  /sys/bus/pnp/devices/00:0f/id:CSC0000
  /sys/bus/pnp/devices/00:0f/resources:state = active
  /sys/bus/pnp/devices/00:0f/resources:io 0x530-0x537
  /sys/bus/pnp/devices/00:0f/resources:io 0x388-0x38b
  /sys/bus/pnp/devices/00:0f/resources:io 0x220-0x22f
  /sys/bus/pnp/devices/00:0f/resources:irq 5
  /sys/bus/pnp/devices/00:0f/resources:dma 1
  /sys/bus/pnp/devices/00:0f/resources:dma 0

  /sys/bus/pnp/devices/00:10/id:CSC0010
  /sys/bus/pnp/devices/00:10/resources:state = active
  /sys/bus/pnp/devices/00:10/resources:io 0x210-0x217

Can't you just register another struct pnp_driver that claims the
CSC0010 device?  E.g., something like:

  static struct pnp_dev *ctrl;
  static int snd_cs423x_ctrl_pnpbios_detect(struct pnp_dev *dev, ...)
  {
	if (pnp_device_is_isapnp(dev)
		return -ENOENT;
	ctrl = dev;
	return 0;
  }

  static const struct pnp_device_id snd_cs423x_ctrl_ids[] = {
	{ .id = "CSC0010" },
  };
  static struct pnp_driver cs423x_ctrl_pnp_driver = {
	.id_table = snd_cs423x_ctrl_ids,
	.probe = snd_cs423x_ctrl_pnpbios_detect,
  };

Obviously that doesn't work for multiple cs423x chips, but I think we
had that problem before.  For ISAPNP, we have the "card" concept to
group the related logical devices.  But I don't see anything similar
in PNPBIOS (maybe I missed it), so I don't see how we could keep track
of multiple PNPBIOS cs423x chips.

Bjorn
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