linux-kernel - Re: [PATCH 4/5] drivers/acpi: elide a non-zero test on a result that is never 0

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Message-Id: <1206431411.3047.45.camel@acpi-hp-zz.sh.intel.com>
Date:	Tue, 25 Mar 2008 15:50:11 +0800
From:	"Zhang, Rui" <rui.zhang@...el.com>
To:	Julia Lawall <julia@...u.dk>
Cc:	"Brown, Len" <len.brown@...el.com>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 4/5] drivers/acpi: elide a non-zero test on a result
	that is never 0


On Tue, 2008-03-25 at 02:10 +0800, Julia Lawall wrote:
> From: Julia Lawall <julia@...u.dk>
> 
> The function thermal_cooling_device_register always returns either a
> valid
> pointer or a value made with ERR_PTR, so a test for non-zero on the
> result
> will always succeed.
>
> The problem was found using the following semantic match.
> (http://www.emn.fr/x-info/coccinelle/)
> //<smpl>
> @a@
> expression E, E1;
> statement S,S1;
> position p;
> @@
> 
> E = thermal_cooling_device_register(...)
> ... when != E = E1
> if@p (E) S else S1
> 
> @n@
> position a.p;
> expression E,E1;
> statement S,S1;
> @@
> 
> E = NULL
> ... when != E = E1
> if@p (E) S else S1
> 
> @depends on !n@
> expression E;
> statement S,S1;
> position a.p;
> @@
> 
> * if@p (E)
>   S else S1
> //</smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
Patch looks correct. Thanks, Julia.
But it misses the same problem in driver/misc/intel_menlow.c.
And the return value of thermal_zone_device_register is also misused.
How about this refreshed patch? :)


Check the return value of thermal zone/cooling device registration correctly.

Signed-off-by: Zhang Rui <rui.zhang@...el.com>
---
 drivers/acpi/fan.c            |    3 +--
 drivers/acpi/processor_core.c |    3 +--
 drivers/acpi/thermal.c        |    2 +-
 drivers/acpi/video.c          |    3 +--
 drivers/misc/intel_menlow.c   |    4 +---
 5 files changed, 5 insertions(+), 10 deletions(-)

Index: linux-2.6/drivers/acpi/fan.c
===================================================================
--- linux-2.6.orig/drivers/acpi/fan.c
+++ linux-2.6/drivers/acpi/fan.c
@@ -259,8 +259,7 @@ static int acpi_fan_add(struct acpi_devi
 	if (IS_ERR(cdev)) {
 		result = PTR_ERR(cdev);
 		goto end;
-	}
-	if (cdev) {
+	} else {
 		printk(KERN_INFO PREFIX
 			"%s is registered as cooling_device%d\n",
 			device->dev.bus_id, cdev->id);
Index: linux-2.6/drivers/acpi/processor_core.c
===================================================================
--- linux-2.6.orig/drivers/acpi/processor_core.c
+++ linux-2.6/drivers/acpi/processor_core.c
@@ -673,8 +673,7 @@ static int __cpuinit acpi_processor_star
 	if (IS_ERR(pr->cdev)) {
 		result = PTR_ERR(pr->cdev);
 		goto end;
-	}
-	if (pr->cdev) {
+	} else {
 		printk(KERN_INFO PREFIX
 			"%s is registered as cooling_device%d\n",
 			device->dev.bus_id, pr->cdev->id);
Index: linux-2.6/drivers/acpi/thermal.c
===================================================================
--- linux-2.6.orig/drivers/acpi/thermal.c
+++ linux-2.6/drivers/acpi/thermal.c
@@ -1125,7 +1125,7 @@ static int acpi_thermal_register_thermal
 			tz->trips.active[i].flags.valid; i++, trips++);
 	tz->thermal_zone = thermal_zone_device_register("ACPI thermal zone",
 					trips, tz, &acpi_thermal_zone_ops);
-	if (!tz->thermal_zone)
+	if (IS_ERR(tz->thermal_zone))
 		return -ENODEV;
 
 	result = sysfs_create_link(&tz->device->dev.kobj,
Index: linux-2.6/drivers/acpi/video.c
===================================================================
--- linux-2.6.orig/drivers/acpi/video.c
+++ linux-2.6/drivers/acpi/video.c
@@ -733,8 +733,7 @@ static void acpi_video_device_find_cap(s
 					device->dev, &video_cooling_ops);
 		if (IS_ERR(device->cdev))
 			return;
-
-		if (device->cdev) {
+		else {
 			printk(KERN_INFO PREFIX
 				"%s is registered as cooling_device%d\n",
 				device->dev->dev.bus_id, device->cdev->id);
Index: linux-2.6/drivers/misc/intel_menlow.c
===================================================================
--- linux-2.6.orig/drivers/misc/intel_menlow.c
+++ linux-2.6/drivers/misc/intel_menlow.c
@@ -173,9 +173,7 @@ static int intel_menlow_memory_add(struc
 	if (IS_ERR(cdev)) {
 		result = PTR_ERR(cdev);
 		goto end;
-	}
-
-	if (cdev) {
+	} else {
 		acpi_driver_data(device) = cdev;
 		result = sysfs_create_link(&device->dev.kobj,
 					&cdev->device.kobj, "thermal_cooling");


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