linux-kernel - Re: [PATCH 4/4] [RFC] hwmon: f71882fg: Add watchdog API for F71808E and F71889

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Date:	Thu, 25 Mar 2010 11:40:15 +0100
From:	Giel van Schijndel <me@...tis.eu>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Hans de Goede <hdegoede@...hat.com>,
	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 4/4] [RFC] hwmon: f71882fg: Add watchdog API for
 F71808E and F71889

On Thu, Mar 25, 2010 at 09:54:50AM +0100, Giel van Schijndel wrote:
> On Wed, Mar 24, 2010 at 03:51:51PM +0000, Alan Cox wrote:
>>> hold on the SIO port range. This would thus interfere with the
>>> operation of the f71882fg driver. I.e. it would prevent the device
>>> probing stage from working, thus preventing it from loading *after*
>>> my in-development watchdog driver.
>> 
>> There are two ways to deal with that really
>> 
>> ... snip ...
>>
>> 2. Fix the kernel request_resource stuff to support a sleeping non
>> exclusive resource so request/free of regions can be used as a resource
>> semaphore by co-operative devices.
>> 
>> #2 is actually not hard but when I did the patch originally it then
>> wasn't needed by the driver I had in mind for other reasons.
>> 
>> See http://groups.google.com/group/linux.kernel/msg/1425fc2aad32e6ea
>> 
>> Maybe its worth resurrecting ?
> 
> In this particular case I most definitely think it's worth resurrecting.
> Using your patch (I had to change the IORESOURCE_MUXED constant's value
> though) I can completely solve the I/O sharing issue for the f71882fg +
> watchdog case with only a single line modification to the f71882fg
> driver.
> 
> ... snip ...

Using Alan's patch and the one following the dashed line I can implement
(and have already done so) a separate watchdog driver for the Fintek
F71808E.

Should I just ask for this patch to be applied together with Alan's?
Then submit the new driver? (I'm a bit new to the non-technical aspects
of Linux kernel development).

========================================================================
hwmon: f71882fg: use a muxed resource lock for the Super I/O port

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.
---
 drivers/hwmon/f71882fg.c |   28 +++++++++++++++-------------
 1 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/hwmon/f71882fg.c b/drivers/hwmon/f71882fg.c
index 7857ed3..e09416d 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)
@@ -2239,17 +2249,10 @@ 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) {
@@ -2306,7 +2309,6 @@ 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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