linux-kernel - [PATCH] ACPI: EC: Fix up fast path check in acpi_ec

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Message-ID: <1708495.96b3J6AjSg@kreacher>
Date:   Mon, 06 Apr 2020 17:49:45 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH] ACPI: EC: Fix up fast path check in acpi_ec_add()

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

The fast path check in acpi_ec_add() is not incorrect, because in
fact acpi_device_hid(device) can be equal to ACPI_ECDT_HID only if
boot_ec is not NULL, but it may confuse static checkers, so change
it to explicitly check boot_ec upfront and use the slow path if
that pointer is NULL.

Link: https://lore.kernel.org/linux-acpi/20200406144217.GA68494@mwanda/
Fixes: 3d9b8dd8320d ("ACPI: EC: Use fast path in acpi_ec_add() for DSDT boot EC")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/ec.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/acpi/ec.c
===================================================================
--- linux-pm.orig/drivers/acpi/ec.c
+++ linux-pm/drivers/acpi/ec.c
@@ -1589,8 +1589,8 @@ static int acpi_ec_add(struct acpi_devic
 	strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
 	strcpy(acpi_device_class(device), ACPI_EC_CLASS);
 
-	if ((boot_ec && boot_ec->handle == device->handle) ||
-	    !strcmp(acpi_device_hid(device), ACPI_ECDT_HID)) {
+	if (boot_ec && (boot_ec->handle == device->handle ||
+	    !strcmp(acpi_device_hid(device), ACPI_ECDT_HID))) {
 		/* Fast path: this device corresponds to the boot EC. */
 		ec = boot_ec;
 	} else {