[PATCH rtw-next v2] wifi: rtw89: acpi: check for _DSM function support before evaluating it

[Rosen Penev]

When the WiFi device has no ACPI companion, or the firmware does not
implement a given rtw89 _DSM function, rtw89_acpi_evaluate_dsm() calls
acpi_evaluate_dsm() anyway. ACPI core then warns on every probe:

  ACPI: \: failed to evaluate _DSM e8c3a8d2-694b-004f-82bd-fe8607803aa7 rev:0 func:10 (0x1001)
  ACPI: \: failed to evaluate _DSM e8c3a8d2-694b-004f-82bd-fe8607803aa7 rev:0 func:6 (0x1001)

Here the handle is NULL, and acpi_evaluate_object() returns
AE_BAD_PARAMETER. All callers already treat failure as "no policy
provided by the platform", so this is only noise.

Bail out early when there is no ACPI handle, as acpi_check_dsm() would
otherwise hit the same warning while querying function 0. Then use
acpi_check_dsm() so that functions the firmware does not advertise fail
quietly at debug level, as rtw89_acpi_evaluate_method() already does.

Seen on an RTL8852BE in a desktop PCIe slot.

Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
---
 v2: check handle separately. Remove Fixes.
 drivers/net/wireless/realtek/rtw89/acpi.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw89/acpi.c b/drivers/net/wireless/realtek/rtw89/acpi.c
index ebb6cf555747..3396d42594b3 100644
--- a/drivers/net/wireless/realtek/rtw89/acpi.c
+++ b/drivers/net/wireless/realtek/rtw89/acpi.c
@@ -372,11 +372,22 @@ int rtw89_acpi_evaluate_dsm(struct rtw89_dev *rtwdev,
 			    enum rtw89_acpi_dsm_func func,
 			    struct rtw89_acpi_dsm_result *res)
 {
+	acpi_handle handle = ACPI_HANDLE(rtwdev->dev);
 	union acpi_object *obj;
 	int ret;
 
-	obj = acpi_evaluate_dsm(ACPI_HANDLE(rtwdev->dev), &rtw89_guid,
-				0, func, NULL);
+	if (!handle) {
+		rtw89_debug(rtwdev, RTW89_DBG_ACPI, "acpi dsm no handle\n");
+		return -ENODEV;
+	}
+
+	if (!acpi_check_dsm(handle, &rtw89_guid, 0, BIT(func))) {
+		rtw89_debug(rtwdev, RTW89_DBG_ACPI,
+			    "acpi dsm func %d not supported\n", func);
+		return -ENOENT;
+	}
+
+	obj = acpi_evaluate_dsm(handle, &rtw89_guid, 0, func, NULL);
 	if (!obj) {
 		rtw89_debug(rtwdev, RTW89_DBG_ACPI,
 			    "acpi dsm fail to evaluate func: %d\n", func);
-- 
2.56.0