[PATCH v2] ACPI: bus: Avoid confusing complaints regarding missing _OSC features

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

The platform firmware on some platforms sets OSC_CAPABILITIES_MASK_ERROR
in _OSC error bits even though it actually acknowledges all of the
requested features which after commit e5322888e6bf ("ACPI: bus: Rework
the handling of \_SB._OSC platform features") causes the kernel to
complain unnecessarily.

Avoid the confusing complaints by explicitly checking for that case
in acpi_osc_handshake().

Fixes: e5322888e6bf ("ACPI: bus: Rework the handling of \_SB._OSC platform features")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Saverio Miroddi <saverio.pub2@gmail.com>
---

v1 -> v2:
   * Apply OSC_ERROR_MASK to retbuf[OSC_QUERY_DWORD] before comparing it
     with OSC_CAPABILITIES_MASK_ERROR (Sashiko)

---
 drivers/acpi/bus.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -335,7 +335,7 @@ static int acpi_osc_handshake(acpi_handl
 		.length = bufsize * sizeof(u32),
 	};
 	struct acpi_buffer output;
-	u32 *retbuf, test;
+	u32 *retbuf, test, errors;
 	guid_t guid;
 	int ret, i;
 
@@ -395,10 +395,18 @@ static int acpi_osc_handshake(acpi_handl
 	 * Clear the feature bits in capbuf[] that have not been acknowledged.
 	 * After that, capbuf[] contains the resultant feature mask.
 	 */
-	for (i = OSC_QUERY_DWORD + 1; i < bufsize; i++)
+	for (i = OSC_QUERY_DWORD + 1, test = 0; i < bufsize; i++) {
+		test |= capbuf[i] & ~retbuf[i];
 		capbuf[i] &= retbuf[i];
+	}
 
-	if (retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK) {
+	errors = retbuf[OSC_QUERY_DWORD] & OSC_ERROR_MASK;
+	/*
+	 * Some platforms set OSC_CAPABILITIES_MASK_ERROR even though they
+	 * acknowledge all of the requested feature, so avoid complaining in
+	 * those cases unless any other error bits are also set.
+	 */
+	if (errors && (test || errors != OSC_CAPABILITIES_MASK_ERROR)) {
 		/*
 		 * Complain about the unexpected errors and print diagnostic
 		 * information related to them.