linux-kernel - Re: [PATCH] ACPI: scan: Add PNP0D80 to the

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Message-ID: <52a2b98c-6bf3-760b-eca9-93cf05fb4877@redhat.com>
Date:   Sat, 5 Dec 2020 16:34:45 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>,
        David Box <david.e.box@...ux.intel.com>
Subject: Re: [PATCH] ACPI: scan: Add PNP0D80 to the _DEP exceptions list

Hi,

On 12/5/20 4:29 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The PNP0D80 ("Windows-compatible System Power Management Controller")
> device ID is used for identifying the special device object providing
> the LPI (Low-power S0 Idle) _DSM interface [1].  That device object
> does not supply any operation regions, but it appears in _DEP lists
> for other devices in the ACPI tables on some systems to enforce
> specific enumeration ordering that does not matter in Linux.
> 
> For this reason, _DEP list entries pointing to the device object whose
> _CID returns PNP0D80 need not be taken into account as real operation
> region dependencies, so add that device ID to the list of device IDs
> for which the matching _DEP list entries should be ignored.
> 
> Accordingly, update the function used for matching device IDs in that
> list to allow it to check _CID as well as _HID and rename it to
> acpi_info_matches_ids().
> 
> Link: https://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf # [1]
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Thank you for doing this, I contemplated doing the exact same
thing but never got around to it.

One small review remark inline:

> ---
>  drivers/acpi/scan.c |   27 +++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -719,25 +719,40 @@ int acpi_device_add(struct acpi_device *
>  /* --------------------------------------------------------------------------
>                                   Device Enumeration
>     -------------------------------------------------------------------------- */
> -static bool acpi_info_matches_hids(struct acpi_device_info *info,
> -				   const char * const hids[])
> +static bool acpi_info_matches_ids(struct acpi_device_info *info,
> +				  const char * const ids[])
>  {
> +	struct acpi_pnp_device_id_list *cid_list = NULL;
>  	int i;
>  
>  	if (!(info->valid & ACPI_VALID_HID))
>  		return false;
>  
> -	for (i = 0; hids[i]; i++) {
> -		if (!strcmp(info->hardware_id.string, hids[i]))
> +	if (info->valid & ACPI_VALID_CID)
> +		cid_list = &info->compatible_id_list;
> +
> +	for (i = 0; ids[i]; i++) {
> +		int j;
> +
> +		if (!strcmp(info->hardware_id.string, ids[i]))
>  			return true;
> +
> +		if (!cid_list)
> +			continue;
> +
> +		for (j = 0; j < cid_list->count; j++) {
> +			if (!strcmp(cid_list->ids[j].string, ids[i]))
> +				return true;
> +		}
>  	}
>  
>  	return false;
>  }
>  
>  /* List of HIDs for which we ignore matching ACPI devices, when checking _DEP lists. */
> -static const char * const acpi_ignore_dep_hids[] = {
> +static const char * const acpi_ignore_dep_ids[] = {
>  	"INT3396", /* Windows System Power Management Controller */

I think this one can be dropped now, I checked my acpidump / dsdt.dsl
collection and 45/45 DSDTs declaring a _HID of INT3396 also added a _CID of
PNP0D80 to this.

Regards,

Hans


> +	"PNP0D80", /* Windows-compatible System Power Management Controller */
>  	NULL
>  };
>  
> @@ -1857,7 +1872,7 @@ static void acpi_device_dep_initialize(s
>  			continue;
>  		}
>  
> -		skip = acpi_info_matches_hids(info, acpi_ignore_dep_hids);
> +		skip = acpi_info_matches_ids(info, acpi_ignore_dep_ids);
>  		kfree(info);
>  
>  		if (skip)
> 
> 
>