linux-kernel - Re: [PATCH 2/3] hwmon: f71882fg: use a muxed resource lock for the Super I/O port

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Message-ID: <20100425103540.GA5185@salidar.me.mortis.eu>
Date:	Sun, 25 Apr 2010 12:35:40 +0200
From:	Giel van Schijndel <me@...tis.eu>
To:	Hans de Goede <hdegoede@...hat.com>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Jonathan Cameron <jic23@....ac.uk>,
	Laurens Leemans <laurens@...nips.com>,
	lm-sensors@...sensors.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hwmon: f71882fg: use a muxed resource lock for the
 Super I/O port

On Thu, Mar 25, 2010 at 02:17:42PM +0100, Giel van Schijndel wrote:
> Sleep while acquiring a resource lock on the Super I/O port. This should
> prevent collisions from causing the hardware probe to fail with -EBUSY.

Fix a bug which caused f71882fg_find() to pretend to be succesfull on
Super I/O ports which didn't have a Fintek chip attached.  This was
caused by returning 0 instead of -ENODEV, adding several 'err = -ENODEV'
statements preceding the 'goto exit' statements fixed this.

Patch follows this line:
========================================================================
Sleep while acquiring a resource lock on the Super I/O port. This should
prevent collisions from causing the hardware probe to fail with -EBUSY.

Signed-off-by: Giel van Schijndel <me@...tis.eu>
---
 drivers/hwmon/f71882fg.c |   32 +++++++++++++++++++-------------
 1 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/hwmon/f71882fg.c b/drivers/hwmon/f71882fg.c
index 7857ed3..85512a7 100644
--- a/drivers/hwmon/f71882fg.c
+++ b/drivers/hwmon/f71882fg.c
@@ -113,7 +113,7 @@ static struct platform_device *f71882fg_pdev;
 /* Super-I/O Function prototypes */
 static inline int superio_inb(int base, int reg);
 static inline int superio_inw(int base, int reg);
-static inline void superio_enter(int base);
+static inline int superio_enter(int base);
 static inline void superio_select(int base, int ld);
 static inline void superio_exit(int base);
 
@@ -883,11 +883,20 @@ static int superio_inw(int base, int reg)
 	return val;
 }
 
-static inline void superio_enter(int base)
+static inline int superio_enter(int base)
 {
+	/* Don't step on other drivers' I/O space by accident */
+	if (!request_muxed_region(base, 2, DRVNAME)) {
+		printk(KERN_ERR DRVNAME ": I/O address 0x%04x already in use\n",
+				(int)base);
+		return -EBUSY;
+	}
+
 	/* according to the datasheet the key must be send twice! */
 	outb(SIO_UNLOCK_KEY, base);
 	outb(SIO_UNLOCK_KEY, base);
+
+	return 0;
 }
 
 static inline void superio_select(int base, int ld)
@@ -899,6 +908,7 @@ static inline void superio_select(int base, int ld)
 static inline void superio_exit(int base)
 {
 	outb(SIO_LOCK_KEY, base);
+	release_region(base, 2);
 }
 
 static inline int fan_from_reg(u16 reg)
@@ -2239,21 +2249,15 @@ static int f71882fg_remove(struct platform_device *pdev)
 static int __init f71882fg_find(int sioaddr, unsigned short *address,
 	struct f71882fg_sio_data *sio_data)
 {
-	int err = -ENODEV;
 	u16 devid;
-
-	/* Don't step on other drivers' I/O space by accident */
-	if (!request_region(sioaddr, 2, DRVNAME)) {
-		printk(KERN_ERR DRVNAME ": I/O address 0x%04x already in use\n",
-				(int)sioaddr);
-		return -EBUSY;
-	}
-
-	superio_enter(sioaddr);
+	int err = superio_enter(sioaddr);
+	if (err)
+		return err;
 
 	devid = superio_inw(sioaddr, SIO_REG_MANID);
 	if (devid != SIO_FINTEK_ID) {
 		pr_debug(DRVNAME ": Not a Fintek device\n");
+		err = -ENODEV;
 		goto exit;
 	}
 
@@ -2280,6 +2284,7 @@ static int __init f71882fg_find(int sioaddr, unsigned short *address,
 	default:
 		printk(KERN_INFO DRVNAME ": Unsupported Fintek device: %04x\n",
 		       (unsigned int)devid);
+		err = -ENODEV;
 		goto exit;
 	}
 
@@ -2290,12 +2295,14 @@ static int __init f71882fg_find(int sioaddr, unsigned short *address,
 
 	if (!(superio_inb(sioaddr, SIO_REG_ENABLE) & 0x01)) {
 		printk(KERN_WARNING DRVNAME ": Device not activated\n");
+		err = -ENODEV;
 		goto exit;
 	}
 
 	*address = superio_inw(sioaddr, SIO_REG_ADDR);
 	if (*address == 0) {
 		printk(KERN_WARNING DRVNAME ": Base address not set\n");
+		err = -ENODEV;
 		goto exit;
 	}
 	*address &= ~(REGION_LENGTH - 1);	/* Ignore 3 LSB */
@@ -2306,7 +2313,6 @@ static int __init f71882fg_find(int sioaddr, unsigned short *address,
 		(int)superio_inb(sioaddr, SIO_REG_DEVREV));
 exit:
 	superio_exit(sioaddr);
-	release_region(sioaddr, 2);
 	return err;
 }
 
-- 
1.6.4.4


-- 
Met vriendelijke groet,
With kind regards,
Giel van Schijndel

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