wifi: iwlwifi: acpi: check DSM func validity

The DSM func 0 (DSM_FUNC_QUERY) returns a bitmap of which
other functions contain valid data, query and check it
before returning other functions data.

Fixes: 9db9349 ("iwlwifi: acpi: support device specific method (DSM)")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220085
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250828095500.881e17ff8f6a.Ic6d92997d9d5fad127919d6e1b830cd3fe944468@changeid

Author: jmberg-intel

drivers/net/wireless/intel/iwlwifi/fw/acpi.c

@@ -169,7 +169,7 @@ int iwl_acpi_get_dsm(struct iwl_fw_runtime *fwrt,
 
 	BUILD_BUG_ON(ARRAY_SIZE(acpi_dsm_size) != DSM_FUNC_NUM_FUNCS);
 
-	if (WARN_ON(func >= ARRAY_SIZE(acpi_dsm_size)))
+	if (WARN_ON(func >= ARRAY_SIZE(acpi_dsm_size) || !func))
 		return -EINVAL;
 
 	expected_size = acpi_dsm_size[func];
@@ -178,6 +178,29 @@ int iwl_acpi_get_dsm(struct iwl_fw_runtime *fwrt,
 	if (expected_size != sizeof(u8) && expected_size != sizeof(u32))
 		return -EOPNOTSUPP;
 
+	if (!fwrt->acpi_dsm_funcs_valid) {
+		ret = iwl_acpi_get_dsm_integer(fwrt->dev, ACPI_DSM_REV,
+					       DSM_FUNC_QUERY,
+					       &iwl_guid, &tmp,
+					       acpi_dsm_size[DSM_FUNC_QUERY]);
+		if (ret) {
+			/* always indicate BIT(0) to avoid re-reading */
+			fwrt->acpi_dsm_funcs_valid = BIT(0);
+			return ret;
+		}
+
+		IWL_DEBUG_RADIO(fwrt, "ACPI DSM validity bitmap 0x%x\n",
+				(u32)tmp);
+		/* always indicate BIT(0) to avoid re-reading */
+		fwrt->acpi_dsm_funcs_valid = tmp | BIT(0);
+	}
+
+	if (!(fwrt->acpi_dsm_funcs_valid & BIT(func))) {
+		IWL_DEBUG_RADIO(fwrt, "ACPI DSM %d not indicated as valid\n",
+				func);
+		return -ENODATA;
+	}
+
 	ret = iwl_acpi_get_dsm_integer(fwrt->dev, ACPI_DSM_REV, func,
 				       &iwl_guid, &tmp, expected_size);
 	if (ret)

drivers/net/wireless/intel/iwlwifi/fw/runtime.h

@@ -113,6 +113,10 @@ struct iwl_txf_iter_data {
  * @phy_filters: specific phy filters as read from WPFC BIOS table
  * @ppag_bios_rev: PPAG BIOS revision
  * @ppag_bios_source: see &enum bios_source
+ * @acpi_dsm_funcs_valid: bitmap indicating which DSM values are valid,
+ *	zero (default initialization) means it hasn't been read yet,
+ *	and BIT(0) is set when it has since function 0 also has this
+ *	bitmap and is always supported
  */
 struct iwl_fw_runtime {
 	struct iwl_trans *trans;
@@ -189,6 +193,10 @@ struct iwl_fw_runtime {
 	bool uats_valid;
 	u8 uefi_tables_lock_status;
 	struct iwl_phy_specific_cfg phy_filters;
+
+#ifdef CONFIG_ACPI
+	u32 acpi_dsm_funcs_valid;
+#endif
 };
 
 void iwl_fw_runtime_init(struct iwl_fw_runtime *fwrt, struct iwl_trans *trans,