linux-kernel - [PATCH 3.16 029/132] hwmon: (pc87427) Use request_muxed

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Message-ID: <lsq.1568989415.488371457@decadent.org.uk>
Date:   Fri, 20 Sep 2019 15:23:35 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "John Garry" <john.garry@...wei.com>,
        "Guenter Roeck" <linux@...ck-us.net>,
        "Kefeng Wang" <wangkefeng.wang@...wei.com>
Subject: [PATCH 3.16 029/132] hwmon: (pc87427) Use request_muxed_region
 for Super-IO accesses

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@...ck-us.net>

commit 755a9b0f8aaa5639ba5671ca50080852babb89ce upstream.

Super-IO accesses may fail on a system with no or unmapped LPC bus.

Also, other drivers may attempt to access the LPC bus at the same time,
resulting in undefined behavior.

Use request_muxed_region() to ensure that IO access on the requested
address space is supported, and to ensure that access by multiple drivers
is synchronized.

Fixes: ba224e2c4f0a7 ("hwmon: New PC87427 hardware monitoring driver")
Reported-by: Kefeng Wang <wangkefeng.wang@...wei.com>
Reported-by: John Garry <john.garry@...wei.com>
Cc: John Garry <john.garry@...wei.com>
Acked-by: John Garry <john.garry@...wei.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/hwmon/pc87427.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/drivers/hwmon/pc87427.c
+++ b/drivers/hwmon/pc87427.c
@@ -106,6 +106,13 @@ static const char *logdev_str[2] = { DRV
 #define LD_IN		1
 #define LD_TEMP		1
 
+static inline int superio_enter(int sioaddr)
+{
+	if (!request_muxed_region(sioaddr, 2, DRVNAME))
+		return -EBUSY;
+	return 0;
+}
+
 static inline void superio_outb(int sioaddr, int reg, int val)
 {
 	outb(reg, sioaddr);
@@ -122,6 +129,7 @@ static inline void superio_exit(int sioa
 {
 	outb(0x02, sioaddr);
 	outb(0x02, sioaddr + 1);
+	release_region(sioaddr, 2);
 }
 
 /*
@@ -1221,7 +1229,11 @@ static int __init pc87427_find(int sioad
 {
 	u16 val;
 	u8 cfg, cfg_b;
-	int i, err = 0;
+	int i, err;
+
+	err = superio_enter(sioaddr);
+	if (err)
+		return err;
 
 	/* Identify device */
 	val = force_id ? force_id : superio_inb(sioaddr, SIOREG_DEVID);