Patch "Revert "ACPI: Pass the same capabilities to the _OSC regardless of the query flag"" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    Revert "ACPI: Pass the same capabilities to the _OSC regardless of the query flag"

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     revert-acpi-pass-the-same-capabilities-to-the-_osc-r.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ff343506ff7ba4f3a68a26da44b42c10661876a7
Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Date:   Wed Mar 16 13:37:44 2022 +0100

    Revert "ACPI: Pass the same capabilities to the _OSC regardless of the query flag"
    
    [ Upstream commit 2ca8e6285250c07a2e5a22ecbfd59b5a4ef73484 ]
    
    Revert commit 159d8c274fd9 ("ACPI: Pass the same capabilities to the
    _OSC regardless of the query flag") which caused legitimate usage
    scenarios (when the platform firmware does not want the OS to control
    certain platform features controlled by the system bus scope _OSC) to
    break and was misguided by some misleading language in the _OSC
    definition in the ACPI specification (in particular, Section 6.2.11.1.3
    "Sequence of _OSC Calls" that contradicts other perts of the _OSC
    definition).
    
    Link: https://lore.kernel.org/linux-acpi/CAJZ5v0iStA0JmO0H3z+VgQsVuQONVjKPpw0F5HKfiq=Gb6B5yw@xxxxxxxxxxxxxx
    Reported-by: Mario Limonciello <Mario.Limonciello@xxxxxxx>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
    Tested-by: Mario Limonciello <mario.limonciello@xxxxxxx>
    Acked-by: Huang Rui <ray.huang@xxxxxxx>
    Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index dd535b4b9a16..3500744e6862 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -332,21 +332,32 @@ static void acpi_bus_osc_negotiate_platform_control(void)
 	if (ACPI_FAILURE(acpi_run_osc(handle, &context)))
 		return;
 
-	kfree(context.ret.pointer);
+	capbuf_ret = context.ret.pointer;
+	if (context.ret.length <= OSC_SUPPORT_DWORD) {
+		kfree(context.ret.pointer);
+		return;
+	}
 
-	/* Now run _OSC again with query flag clear */
+	/*
+	 * Now run _OSC again with query flag clear and with the caps
+	 * supported by both the OS and the platform.
+	 */
 	capbuf[OSC_QUERY_DWORD] = 0;
+	capbuf[OSC_SUPPORT_DWORD] = capbuf_ret[OSC_SUPPORT_DWORD];
+	kfree(context.ret.pointer);
 
 	if (ACPI_FAILURE(acpi_run_osc(handle, &context)))
 		return;
 
 	capbuf_ret = context.ret.pointer;
-	osc_sb_apei_support_acked =
-		capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_APEI_SUPPORT;
-	osc_pc_lpi_support_confirmed =
-		capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_PCLPI_SUPPORT;
-	osc_sb_native_usb4_support_confirmed =
-		capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_NATIVE_USB4_SUPPORT;
+	if (context.ret.length > OSC_SUPPORT_DWORD) {
+		osc_sb_apei_support_acked =
+			capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_APEI_SUPPORT;
+		osc_pc_lpi_support_confirmed =
+			capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_PCLPI_SUPPORT;
+		osc_sb_native_usb4_support_confirmed =
+			capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_NATIVE_USB4_SUPPORT;
+	}
 
 	kfree(context.ret.pointer);
 }