[PATCH] acpi: remove length check for large registers

[PATCH] acpi: remove length check for large registers

[Linn Crosetto]

The legacy bit width field in the Generic Address Structure is 1 byte,
limiting the reportable register width to 255 bits. Larger registers
will cause a length mismatch warning to be printed in
acpi_tb_validate_fadt().

To avoid the warning, disable the length mismatch check for registers
larger than 255 bits.

Signed-off-by: Linn Crosetto <linn@hp.com>
---
 drivers/acpi/acpica/tbfadt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/acpi/acpica/tbfadt.c b/drivers/acpi/acpica/tbfadt.c
index 74181bf..e87abcd 100644
--- a/drivers/acpi/acpica/tbfadt.c
+++ b/drivers/acpi/acpica/tbfadt.c
@@ -561,6 +561,7 @@ static void acpi_tb_validate_fadt(void)
 		 * legacy length field and the corresponding 64-bit X length field.
 		 */
 		if (address64->address &&
+		    ACPI_MUL_8(length) <= ACPI_UINT8_MAX &&
 		    (address64->bit_width != ACPI_MUL_8(length))) {
 			ACPI_BIOS_WARNING((AE_INFO,
 					   "32/64X length mismatch in FADT/%s: %u/%u",
-- 
1.7.11.3

RE: [PATCH] acpi: remove length check for large registers

[Moore, Robert]

Linn,

Can you explain in a bit more detail what brings this up?

I'm aware of the limitation of the generic address structure, but we are forced by the (current) ACPI specification to use it if it is present for a given register.

Thanks,
Bob


> -----Original Message-----
> From: Linn Crosetto [mailto:linn@hp.com]
> Sent: Friday, March 15, 2013 12:56 PM
> To: rjw@sisk.pl; Moore, Robert; ming.m.lin@intel.com; Zheng, Lv; linux-
> acpi@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org; Linn Crosetto
> Subject: [PATCH] acpi: remove length check for large registers
> 
> The legacy bit width field in the Generic Address Structure is 1 byte,
> limiting the reportable register width to 255 bits. Larger registers will
> cause a length mismatch warning to be printed in acpi_tb_validate_fadt().
> 
> To avoid the warning, disable the length mismatch check for registers
> larger than 255 bits.
> 
> Signed-off-by: Linn Crosetto <linn@hp.com>
> ---
>  drivers/acpi/acpica/tbfadt.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/acpi/acpica/tbfadt.c b/drivers/acpi/acpica/tbfadt.c
> index 74181bf..e87abcd 100644
> --- a/drivers/acpi/acpica/tbfadt.c
> +++ b/drivers/acpi/acpica/tbfadt.c
> @@ -561,6 +561,7 @@ static void acpi_tb_validate_fadt(void)
>  		 * legacy length field and the corresponding 64-bit X length
> field.
>  		 */
>  		if (address64->address &&
> +		    ACPI_MUL_8(length) <= ACPI_UINT8_MAX &&
>  		    (address64->bit_width != ACPI_MUL_8(length))) {
>  			ACPI_BIOS_WARNING((AE_INFO,
>  					   "32/64X length mismatch in FADT/%s:
> %u/%u",
> --
> 1.7.11.3

Re: [PATCH] acpi: remove length check for large registers

[Linn Crosetto]

On Fri, Mar 15, 2013 at 08:50:45PM +0000, Moore, Robert wrote:
> Can you explain in a bit more detail what brings this up?
> 
> I'm aware of the limitation of the generic address structure, but we are forced by the (current) ACPI specification to use it if it is present for a given register.

A system with a GPE block bit_width of 256 triggers it. In this case, the length
check can never succeed.

Thanks,
Linn

RE: [PATCH] acpi: remove length check for large registers

[Moore, Robert]

Linn,

We will integrate this change into ACPICA for the next release, later in March 2013.
Thanks,
Bob


> -----Original Message-----
> From: Linn Crosetto [mailto:linn@hp.com]
> Sent: Friday, March 15, 2013 12:56 PM
> To: rjw@sisk.pl; Moore, Robert; ming.m.lin@intel.com; Zheng, Lv; linux-
> acpi@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org; Linn Crosetto
> Subject: [PATCH] acpi: remove length check for large registers
> 
> The legacy bit width field in the Generic Address Structure is 1 byte,
> limiting the reportable register width to 255 bits. Larger registers will
> cause a length mismatch warning to be printed in acpi_tb_validate_fadt().
> 
> To avoid the warning, disable the length mismatch check for registers
> larger than 255 bits.
> 
> Signed-off-by: Linn Crosetto <linn@hp.com>
> ---
>  drivers/acpi/acpica/tbfadt.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/acpi/acpica/tbfadt.c b/drivers/acpi/acpica/tbfadt.c
> index 74181bf..e87abcd 100644
> --- a/drivers/acpi/acpica/tbfadt.c
> +++ b/drivers/acpi/acpica/tbfadt.c
> @@ -561,6 +561,7 @@ static void acpi_tb_validate_fadt(void)
>  		 * legacy length field and the corresponding 64-bit X length
> field.
>  		 */
>  		if (address64->address &&
> +		    ACPI_MUL_8(length) <= ACPI_UINT8_MAX &&
>  		    (address64->bit_width != ACPI_MUL_8(length))) {
>  			ACPI_BIOS_WARNING((AE_INFO,
>  					   "32/64X length mismatch in FADT/%s:
> %u/%u",
> --
> 1.7.11.3