linux-kernel - Re: [PATCH] PNPACPI: cope with invalid device IDs

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Message-Id: <201006041123.25141.bjorn.helgaas@hp.com>
Date:	Fri, 4 Jun 2010 11:23:22 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Len Brown <lenb@...nel.org>
Subject: Re: [PATCH] PNPACPI: cope with invalid device IDs

On Friday, June 04, 2010 02:04:32 am Dmitry Torokhov wrote:
> If primary ID (HID) is invalid try locating first valid ID on compatible
> ID list before giving up. This helps, for example, to recognize i8042 AUX
> port on Sony Vaio VPCZ1 which uses SNYSYN0003 as HID.

Is there a bugzilla report or mailing list discussion you could point
to here (in the changelog)?

> Tested-by: Jan-Hendrik Zab <jan@....name>
> Signed-off-by: Dmitry Torokhov <dtor@...l.ru>
> ---
> 
>  drivers/pnp/pnpacpi/core.c |   27 +++++++++++++++++++++++----
>  1 files changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
> index f7ff628..1bf1677 100644
> --- a/drivers/pnp/pnpacpi/core.c
> +++ b/drivers/pnp/pnpacpi/core.c
> @@ -28,7 +28,7 @@
>  #include "../base.h"
>  #include "pnpacpi.h"
>  
> -static int num = 0;
> +static int num;

Unrelated change, but OK by me :-)

>  /* We need only to blacklist devices that have already an acpi driver that
>   * can't use pnp layer. We don't need to blacklist device that are directly
> @@ -157,11 +157,24 @@ struct pnp_protocol pnpacpi_protocol = {
>  };
>  EXPORT_SYMBOL(pnpacpi_protocol);
>  
> +static char *pnpacpi_get_id(struct acpi_device *device)
> +{
> +	struct acpi_hardware_id *id;
> +
> +	list_for_each_entry(id, &device->pnp.ids, list) {
> +		if (ispnpidacpi(id->id))
> +			return id->id;
> +	}
> +
> +	return NULL;
> +}
> +
>  static int __init pnpacpi_add_device(struct acpi_device *device)
>  {
>  	acpi_handle temp = NULL;
>  	acpi_status status;
>  	struct pnp_dev *dev;
> +	char *pnpid;
>  	struct acpi_hardware_id *id;
>  
>  	/*
> @@ -169,11 +182,17 @@ static int __init pnpacpi_add_device(struct acpi_device *device)
>  	 * driver should not be loaded.
>  	 */
>  	status = acpi_get_handle(device->handle, "_CRS", &temp);
> -	if (ACPI_FAILURE(status) || !ispnpidacpi(acpi_device_hid(device)) ||
> -	    is_exclusive_device(device) || (!device->status.present))
> +	if (ACPI_FAILURE(status))
> +		return 0;
> +
> +	pnpid = pnpacpi_get_id(device);
> +	if (!pnpid)
> +		return 0;

This part (run ispnpidacpi() on all _HIDs & _CIDs, not just on _HID,
so we'll now build a PNPACPI device for things with an invalid _HID
but a valid _CID) makes sense to me and is probably required for the
i8042 PNP driver to claim the device.

> +
> +	if (!is_exclusive_device(device) || !device->status.present)
>  		return 0;
>  
> -	dev = pnp_alloc_dev(&pnpacpi_protocol, num, acpi_device_hid(device));
> +	dev = pnp_alloc_dev(&pnpacpi_protocol, num, pnpid);

I'm curious about this part.  Does it fix something?

Let's say this device has _HID=SNYSYN0003, _CID=PNP0F13.

Previously, we didn't make a PNP device at all because SNYSYN0003 is
invalid.  Now, we'll make a device, exclude SNYSYN0003 from the PNP ID
list, and it looks like the loop farther down will add PNP0f13 again,
so we'll end up with "PNP0f13 PNP0f13" (I think I mentioned this when
reviewing an earlier version of the patch :-)).

With the original pnp_alloc_dev(acpi_device_hid()) call, we'll probably
end up with "SNYsyn0 PNP0f13".  That's clearly wrong, too.

For now, I think the best fix is to keep this pnp_alloc_dev() call change
and adjust the loop so it doesn't add "pnpid" again, so we end up with
just "PNP0f13".

In the long term, I wonder if it'd be better to quit checking the ID for
validity and make pnp_id.id a pointer rather than an array, so we could
have "SNYSYN0003 PNP0f13" as PNP IDs for this device.  I bet that's what
Windows does. 

Bjorn
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