Re: [PATCH 2/3] Introduce acpi_root_table=rsdt boot param and dmi list to force rsdt

[Len Brown <lenb@kernel.org>]

I find it hard to believe that Windows has a DMI entry for the R40e
to use the RSDT instead of the XSDT.

We should find out why the XSDT is disqualified on that machine
and do the same in Linux so that the R40e and any other similar
machines do not need DMI entries.

-Len

On Thursday 08 May 2008, Thomas Renninger wrote:
> Introduce acpi_root_table=rsdt boot param and dmi list to force rsdt
> 
> Signed-off-by: Thomas Renninger <trenn@suse.de>
> Tested-by: Mark Doughty <me@markdoughty.co.uk>
> 
> 
> ---
>  Documentation/kernel-parameters.txt |    5 +++++
>  drivers/acpi/tables.c               |   23 +++++++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> Index: linux-acpi-2.6_video_native_vs_vendor/drivers/acpi/tables.c
> ===================================================================
> --- linux-acpi-2.6_video_native_vs_vendor.orig/drivers/acpi/tables.c
> +++ linux-acpi-2.6_video_native_vs_vendor/drivers/acpi/tables.c
> @@ -32,6 +32,7 @@
>  #include <linux/errno.h>
>  #include <linux/acpi.h>
>  #include <linux/bootmem.h>
> +#include <linux/dmi.h>
>  
>  #define PREFIX			"ACPI: "
>  
> @@ -282,6 +283,23 @@ static void __init check_multiple_madt(v
>  	return;
>  }
>  
> +static struct dmi_system_id acpi_rsdt_dmi_table[] = {
> +	{
> +	    .ident = "ThinkPad ",
> +	    .matches = {
> +		DMI_MATCH(DMI_BIOS_VENDOR, "IBM"),
> +		DMI_MATCH(DMI_BIOS_VERSION, "1SET")},
> +	},
> +};
> +
> +static int __init acpi_force_rsdt(char *opt)
> +{
> +	if (!strcmp(opt, "rsdt"))
> +		acpi_gbl_force_rsdt = 1;
> +	return 0;
> +}
> +early_param("acpi_root_table", acpi_force_rsdt);
> +
>  /*
>   * acpi_table_init()
>   *
> @@ -293,6 +311,11 @@ static void __init check_multiple_madt(v
>  
>  int __init acpi_table_init(void)
>  {
> +	if (dmi_check_system(acpi_rsdt_dmi_table))
> +		acpi_gbl_force_rsdt = 1;
> +	if (acpi_gbl_force_rsdt)
> +		printk(KERN_INFO "Using RSDT as ACPI root table\n");
> +
>  	acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0);
>  	check_multiple_madt();
>  	return 0;
> Index: linux-acpi-2.6_video_native_vs_vendor/Documentation/kernel-parameters.txt
> ===================================================================
> --- linux-acpi-2.6_video_native_vs_vendor.orig/Documentation/kernel-parameters.txt
> +++ linux-acpi-2.6_video_native_vs_vendor/Documentation/kernel-parameters.txt
> @@ -230,6 +230,11 @@ and is between 256 and 4096 characters.
>  			to assume that this machine's pmtimer latches its value
>  			and always returns good values.
>  
> +	acpi_root_table=	[X86,ACPI]
> +			{ rsdt }
> +			rsdt: If RSDP contains a non-NULL RSDT address, take it
> +			      for fetching ACPI tables (instead of XSDT)
> +
>  	agp=		[AGP]
>  			{ off | try_unsupported }
>  			off: disable AGP support
> 
> 
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