acpi: remove length check for large registers

PATCH In review Linn Crosetto 2 participants 4 messages Mar 15, 2013 – Mar 19, 2013

Subsystems (2)

ACPI ACPI component architecture (acpica)

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Linn Crosetto

author

2013-03-15 19:57 UTC #0 lore raw

PATCH 1/1 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 <[email protected]>

---
 drivers/acpi/acpica/tbfadt.c | 1 +
 1 file changed, 1 insertion(+)

drivers/acpi/acpica/tbfadt.c +1 -0

index 74181bf..e87abcd 100644
@@ -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",

Signature · 1 line

1.7.11.3

Moore, Robert

2013-03-15 20:50 UTC #1 lore raw

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

Quoted 36 lines

-----Original Message-----
From: Linn Crosetto [mailto:[email protected]]
Sent: Friday, March 15, 2013 12:56 PM
To: [email protected]; Moore, Robert; [email protected]; Zheng, Lv; linux- [email protected]
Cc: [email protected]; 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 <[email protected]>
---
 drivers/acpi/acpica/tbfadt.c | 1 +
 1 file changed, 1 insertion(+)
drivers/acpi/acpica/tbfadt.c +0 -0
index 74181bf..e87abcd 100644
@@ -561,6 +561,7 @@ static void acpi_tb_validate_fadt(void)
 		 * legacy length field and the corresponding 64-bit X length
field.
drivers/acpi/acpica/tbfadt.c +1 -0
 		 */
 		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

Linn Crosetto

author

2013-03-15 21:18 UTC #2 lore raw

Quoted 3 lines · Robert

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

Moore, Robert

2013-03-19 18:49 UTC #3 lore raw

In reply to Linn Crosetto

Linn,

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

Quoted 36 lines

-----Original Message-----
From: Linn Crosetto [mailto:[email protected]]
Sent: Friday, March 15, 2013 12:56 PM
To: [email protected]; Moore, Robert; [email protected]; Zheng, Lv; linux- [email protected]
Cc: [email protected]; 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 <[email protected]>
---
 drivers/acpi/acpica/tbfadt.c | 1 +
 1 file changed, 1 insertion(+)
drivers/acpi/acpica/tbfadt.c +0 -0
index 74181bf..e87abcd 100644
@@ -561,6 +561,7 @@ static void acpi_tb_validate_fadt(void)
 		 * legacy length field and the corresponding 64-bit X length
field.
drivers/acpi/acpica/tbfadt.c +1 -0
 		 */
 		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