Minor overhaul of SMBus support:

- Change smbus_callback() to pass a void * rather than caddr_t.
- Change smbus_bread() to pass a pointer to the count and have it be an
  in/out parameter.  The input is the size of the buffer (same as before),
  but on return it will contain the actual amount of data read back from
  the bus.  Note that this value may be larger than the input value.  It
  is up to the caller to treat this as an error if desired.
- Change the SMB_BREAD ioctl to write out the updated struct smbcmd which
  will contain the actual number of bytes read in the 'count' field.  To
  preserve the previous ABI, the old ioctl value is mapped to SMB_OLD_BREAD
  which doesn't copy the updated smbcmd back out to userland.  I doubt anyone
  actually used the old BREAD anyway as it was rediculous to do a bulk-read
  but not tell the using program how much data was actually read.
- Make the smbus driver and devclass public in the smbus module and
  push all the DRIVER_MODULE()'s for attaching the smbus driver to
  various foosmb drivers out into the foosmb modules.  This makes all
  the foosmb logic centralized and allows new foosmb modules to be
  self-contained w/o having to hack smbus.c everytime a new smbus driver
  is added.
- Add a new SMB_EINVAL error bit and use it in place of EINVAL to return
  an error for bad arguments (such as invalid counts for bread and bwrite).
- Map SMB bus error bits to EIO in smbus_error().
- Make the smbus driver call bus_generic_probe() and require child drivers
  such as smb(4) to create device_t's via identify routines.  Previously,
  smbus just created one anonymous device during attach, and if you had
  multiple drivers that could attach it was just random chance as to which
  driver got to probe for the sole device_t first.
- Add a mutex to the smbus(4) softc and use it in place of dummy splhigh()
  to protect the 'owner' field and perform necessary synchronization for
  smbus_request_bus() and smbus_release_bus().
- Change the bread() and bwrite() methods of alpm(4), amdpm(4), and
  viapm(4) to only perform a single transaction and not try to use a
  loop of multiple transactions for a large request.  The framing and
  commands to use for a large transaction depend on the upper-layer
  protocol (such as SSIF for IPMI over SMBus) from what I can tell, and the
  smb(4) driver never allowed bulk read/writes of more than 32-bytes
  anyway.  The other smb drivers only performed single transactions.
- Fix buffer overflows in the bread() methods of ichsmb(4), alpm(4),
  amdpm(4), amdsmb(4), intpm(4), and nfsmb(4).
- Use SMB_xxx errors in viapm(4).
- Destroy ichsmb(4)'s mutex after bus_generic_detach() to avoid problems
  from child devices making smb upcalls that would use the mutex during
  their detach methods.

MFC after:	1 week
Reviewed by:	jmg (mostly)

16 files changed, 327 insertions, 281 deletions

diff --git a/sys/dev/bktr/bktr_i2c.c b/sys/dev/bktr/bktr_i2c.c
index 20802f4..0bf5262 100644
--- a/sys/dev/bktr/bktr_i2c.c
+++ b/sys/dev/bktr/bktr_i2c.c
@@ -119,7 +119,7 @@ error:
 	return (error);
 }
 
-int bti2c_smb_callback(device_t dev, int index, caddr_t *data)
+int bti2c_smb_callback(device_t dev, int index, void *data)
 {
 	struct bktr_softc *bktr_sc = (struct bktr_softc *)device_get_softc(dev);
 	struct bktr_i2c_softc *sc = &bktr_sc->i2c_sc;
@@ -338,4 +338,6 @@ bti2c_smb_readb(device_t dev, u_char slave, char cmd, char *byte)
 	return (0);
 }
 
+DRIVER_MODULE(smbus, bktr, smbus_driver, smbus_devclass, 0, 0);
+
 #endif /* defined(BKTR_USE_FREEBSD_SMBUS) */
diff --git a/sys/dev/ichsmb/ichsmb.c b/sys/dev/ichsmb/ichsmb.c
index 53a91d0..18aa32b 100644
--- a/sys/dev/ichsmb/ichsmb.c
+++ b/sys/dev/ichsmb/ichsmb.c
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/kernel.h>
 #include <sys/errno.h>
 #include <sys/lock.h>
+#include <sys/module.h>
 #include <sys/mutex.h>
 #include <sys/syslog.h>
 #include <sys/bus.h>
@@ -136,7 +137,7 @@ ichsmb_attach(device_t dev)
 ********************************************************************/
 
 int 
-ichsmb_callback(device_t dev, int index, caddr_t data)
+ichsmb_callback(device_t dev, int index, void *data)
 {
 	int smb_error = 0;
 
@@ -381,7 +382,7 @@ ichsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 	KASSERT(sc->ich_cmd == -1,
 	    ("%s: ich_cmd=%d\n", __func__ , sc->ich_cmd));
 	if (count < 1 || count > 32)
-		return (EINVAL);
+		return (SMB_EINVAL);
 	bcopy(buf, sc->block_data, count);
 	sc->block_count = count;
 	sc->block_index = 1;
@@ -403,7 +404,7 @@ ichsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 }
 
 int
-ichsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+ichsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	const sc_p sc = device_get_softc(dev);
 	int smb_error;
@@ -411,10 +412,10 @@ ichsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 	DBG("slave=0x%02x cmd=0x%02x count=%d\n", slave, (u_char)cmd, count);
 	KASSERT(sc->ich_cmd == -1,
 	    ("%s: ich_cmd=%d\n", __func__ , sc->ich_cmd));
-	if (count < 1 || count > 32)
-		return (EINVAL);
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 	bzero(sc->block_data, sizeof(sc->block_data));
-	sc->block_count = count;
+	sc->block_count = 0;
 	sc->block_index = 0;
 	sc->block_write = 0;
 
@@ -423,11 +424,13 @@ ichsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 	bus_space_write_1(sc->io_bst, sc->io_bsh, ICH_XMIT_SLVA,
 	    (slave << 1) | ICH_XMIT_SLVA_READ);
 	bus_space_write_1(sc->io_bst, sc->io_bsh, ICH_HST_CMD, cmd);
-	bus_space_write_1(sc->io_bst, sc->io_bsh, ICH_D0, count); /* XXX? */
+	bus_space_write_1(sc->io_bst, sc->io_bsh, ICH_D0, *count); /* XXX? */
 	bus_space_write_1(sc->io_bst, sc->io_bsh, ICH_HST_CNT,
 	    ICH_HST_CNT_START | ICH_HST_CNT_INTREN | sc->ich_cmd);
-	if ((smb_error = ichsmb_wait(sc)) == SMB_ENOERR)
-		bcopy(sc->block_data, buf, sc->block_count);
+	if ((smb_error = ichsmb_wait(sc)) == SMB_ENOERR) {
+		bcopy(sc->block_data, buf, min(sc->block_count, *count));
+		*count = sc->block_count;
+	}
 	mtx_unlock(&sc->mutex);
 	DBG("smb_error=%d\n", smb_error);
 #if ICHSMB_DEBUG
@@ -669,14 +672,20 @@ ichsmb_release_resources(sc_p sc)
 	}
 }
 
-int ichsmb_detach(device_t dev)
+int
+ichsmb_detach(device_t dev)
 {
 	const sc_p sc = device_get_softc(dev);
+	int error;
 
-	mtx_destroy(&sc->mutex);
-	bus_generic_detach(dev);
+	error = bus_generic_detach(dev);
+	if (error)
+		return (error);
 	device_delete_child(dev, sc->smb);
 	ichsmb_release_resources(sc);
+	mtx_destroy(&sc->mutex);
 	
 	return 0;
 }
+
+DRIVER_MODULE(smbus, ichsmb, smbus_driver, smbus_devclass, 0, 0);
diff --git a/sys/dev/iicbus/iicsmb.c b/sys/dev/iicbus/iicsmb.c
index c2d45d4..0788184 100644
--- a/sys/dev/iicbus/iicsmb.c
+++ b/sys/dev/iicbus/iicsmb.c
@@ -83,7 +83,7 @@ static int iicsmb_detach(device_t);
 static void iicsmb_identify(driver_t *driver, device_t parent);
 
 static void iicsmb_intr(device_t dev, int event, char *buf);
-static int iicsmb_callback(device_t dev, int index, caddr_t data);
+static int iicsmb_callback(device_t dev, int index, void *data);
 static int iicsmb_quick(device_t dev, u_char slave, int how);
 static int iicsmb_sendb(device_t dev, u_char slave, char byte);
 static int iicsmb_recvb(device_t dev, u_char slave, char *byte);
@@ -93,7 +93,7 @@ static int iicsmb_readb(device_t dev, u_char slave, char cmd, char *byte);
 static int iicsmb_readw(device_t dev, u_char slave, char cmd, short *word);
 static int iicsmb_pcall(device_t dev, u_char slave, char cmd, short sdata, short *rdata);
 static int iicsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf);
-static int iicsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf);
+static int iicsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf);
 
 static devclass_t iicsmb_devclass;
 
@@ -247,7 +247,7 @@ end:
 }
 
 static int
-iicsmb_callback(device_t dev, int index, caddr_t data)
+iicsmb_callback(device_t dev, int index, void *data)
 {
 	device_t parent = device_get_parent(dev);
 	int error = 0;
@@ -482,7 +482,7 @@ error:
 }
 
 static int
-iicsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+iicsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	device_t parent = device_get_parent(dev);
 	int error, sent, read;
@@ -496,9 +496,10 @@ iicsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 	if ((error = iicbus_repeated_start(parent, slave | LSB, IICBUS_TIMEOUT)))
 		goto error;
 
-	if ((error = iicbus_read(parent, buf, (int)count, &read,
+	if ((error = iicbus_read(parent, buf, (int)*count, &read,
 						IIC_LAST_READ, IICBUS_TIMEOUT)))
 		goto error;
+	*count = read;
 
 error:
 	iicbus_stop(parent);
@@ -506,6 +507,7 @@ error:
 }
 
 DRIVER_MODULE(iicsmb, iicbus, iicsmb_driver, iicsmb_devclass, 0, 0);
+DRIVER_MODULE(smbus, iicsmb, smbus_driver, smbus_devclass, 0, 0);
 MODULE_DEPEND(iicsmb, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER);
 MODULE_DEPEND(iicsmb, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
 MODULE_VERSION(iicsmb, 1);
diff --git a/sys/dev/smbus/smb.c b/sys/dev/smbus/smb.c
index ca4fbe6..e5944bd 100644
--- a/sys/dev/smbus/smb.c
+++ b/sys/dev/smbus/smb.c
@@ -55,6 +55,7 @@ struct smb_softc {
 #define IIC_DEVICE(unit) \
 	(devclass_get_device(smb_devclass, (unit)))
 
+static void smb_identify(driver_t *driver, device_t parent);
 static int smb_probe(device_t);
 static int smb_attach(device_t);
 static int smb_detach(device_t);
@@ -63,6 +64,7 @@ static devclass_t smb_devclass;
 
 static device_method_t smb_methods[] = {
 	/* device interface */
+	DEVMETHOD(device_identify,	smb_identify),
 	DEVMETHOD(device_probe,		smb_probe),
 	DEVMETHOD(device_attach,	smb_attach),
 	DEVMETHOD(device_detach,	smb_detach),
@@ -92,6 +94,14 @@ static struct cdevsw smb_cdevsw = {
 	.d_name =	"smb",
 };
 
+static void
+smb_identify(driver_t *driver, device_t parent)
+{
+
+	if (device_find_child(parent, "smb", -1) == NULL)
+		BUS_ADD_CHILD(parent, 0, "smb", -1);
+}
+
 static int
 smb_probe(device_t dev)
 {
@@ -171,6 +181,7 @@ smbioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags, struct thread *t
 	device_t smbdev = IIC_DEVICE(minor(dev));
 	int error;
 	short w;
+	u_char count;
 	char c;
 
 	if (sc == NULL)
@@ -259,15 +270,17 @@ smbioctl(struct cdev *dev, u_long cmd, caddr_t data, int flags, struct thread *t
 		}
 		break;
 
+	case SMB_OLD_BREAD:
 	case SMB_BREAD:
 		if (s->count && s->data.byte_ptr) {
-			if (s->count > SMB_MAXBLOCKSIZE)
-				s->count = SMB_MAXBLOCKSIZE;
+			count = min(s->count, SMB_MAXBLOCKSIZE);
 			error = smbus_error(smbus_bread(parent, s->slave,
-						s->cmd, s->count, buf));
+						s->cmd, &count, buf));
 			if (error)
 				break;
-			error = copyout(buf, s->data.byte_ptr, s->count);
+			error = copyout(buf, s->data.byte_ptr,
+			    min(count, s->count));
+			s->count = count;
 		}
 		break;
 		
diff --git a/sys/dev/smbus/smb.h b/sys/dev/smbus/smb.h
index 387515f..32347f8 100644
--- a/sys/dev/smbus/smb.h
+++ b/sys/dev/smbus/smb.h
@@ -64,6 +64,7 @@ struct smbcmd {
 #define SMB_READW	_IOW('i', 8, struct smbcmd)
 #define SMB_PCALL	_IOW('i', 9, struct smbcmd)
 #define SMB_BWRITE	_IOW('i', 10, struct smbcmd)
-#define SMB_BREAD	_IOW('i', 11, struct smbcmd)
+#define SMB_OLD_BREAD	_IOW('i', 11, struct smbcmd)
+#define SMB_BREAD	_IOWR('i', 11, struct smbcmd)
 
 #endif
diff --git a/sys/dev/smbus/smbconf.c b/sys/dev/smbus/smbconf.c
index 8a85009..06d225a 100644
--- a/sys/dev/smbus/smbconf.c
+++ b/sys/dev/smbus/smbconf.c
@@ -30,7 +30,9 @@
 __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/lock.h>
 #include <sys/module.h>
+#include <sys/mutex.h>
 #include <sys/bus.h>
 
 #include <dev/smbus/smbconf.h>
@@ -43,13 +45,13 @@ __FBSDID("$FreeBSD$");
 void
 smbus_intr(device_t bus, u_char devaddr, char low, char high, int error)
 {
-	struct smbus_softc *sc = (struct smbus_softc *)device_get_softc(bus);
+	struct smbus_softc *sc = device_get_softc(bus);
 
 	/* call owner's intr routine */
+	mtx_lock(&sc->lock);
 	if (sc->owner)
 		SMBUS_INTR(sc->owner, devaddr, low, high, error);
-
-	return;
+	mtx_unlock(&sc->lock);
 }
 
 /*
@@ -65,17 +67,18 @@ smbus_error(int smb_error)
 	if (smb_error == SMB_ENOERR)
 		return (0);
 	
-	if (smb_error & (SMB_ENOTSUPP)) {
+	if (smb_error & (SMB_ENOTSUPP))
 		error = ENODEV;
-	} else if (smb_error & (SMB_ENOACK)) {
+	else if (smb_error & (SMB_ENOACK))
 		error = ENXIO;
-	} else if (smb_error & (SMB_ETIMEOUT)) {
+	else if (smb_error & (SMB_ETIMEOUT))
 		error = EWOULDBLOCK;
-	} else if (smb_error & (SMB_EBUSY)) {
+	else if (smb_error & (SMB_EBUSY))
 		error = EBUSY;
-	} else {
+	else if (smb_error & (SMB_EABORT | SMB_EBUSERR | SMB_ECOLLI))
+		error = EIO;
+	else
 		error = EINVAL;
-	}
 
 	return (error);
 }
@@ -86,16 +89,16 @@ smbus_poll(struct smbus_softc *sc, int how)
 	int error;
 
 	switch (how) {
-	case (SMB_WAIT | SMB_INTR):
-		error = tsleep(sc, SMBPRI|PCATCH, "smbreq", 0);
+	case SMB_WAIT | SMB_INTR:		
+		error = msleep(sc, &sc->lock, SMBPRI|PCATCH, "smbreq", 0);
 		break;
 
-	case (SMB_WAIT | SMB_NOINTR):
-		error = tsleep(sc, SMBPRI, "smbreq", 0);
+	case SMB_WAIT | SMB_NOINTR:
+		error = msleep(sc, &sc->lock, SMBPRI, "smbreq", 0);
 		break;
 
 	default:
-		return (EWOULDBLOCK);
+		error = EWOULDBLOCK;
 		break;
 	}
 
@@ -112,35 +115,38 @@ smbus_poll(struct smbus_softc *sc, int how)
 int
 smbus_request_bus(device_t bus, device_t dev, int how)
 {
-	struct smbus_softc *sc = (struct smbus_softc *)device_get_softc(bus);
-	int s, error = 0;
+	struct smbus_softc *sc = device_get_softc(bus);
+	device_t parent;
+	int error;
 
 	/* first, ask the underlying layers if the request is ok */
+	parent = device_get_parent(bus);
+	mtx_lock(&sc->lock);
 	do {
-		error = SMBUS_CALLBACK(device_get_parent(bus),
-						SMB_REQUEST_BUS, (caddr_t)&how);
+		mtx_unlock(&sc->lock);
+		error = SMBUS_CALLBACK(parent, SMB_REQUEST_BUS, &how);
+		mtx_lock(&sc->lock);
+
 		if (error)
 			error = smbus_poll(sc, how);
 	} while (error == EWOULDBLOCK);
 
-	while (!error) {
-		s = splhigh();	
-		if (sc->owner && sc->owner != dev) {
-			splx(s);
-
+	while (error == 0) {
+		if (sc->owner && sc->owner != dev)
 			error = smbus_poll(sc, how);
-		} else {
+		else {
 			sc->owner = dev;
-
-			splx(s);
-			return (0);
+			break;
 		}
 
 		/* free any allocated resource */
-		if (error)
-			SMBUS_CALLBACK(device_get_parent(bus), SMB_RELEASE_BUS,
-					(caddr_t)&how);
+		if (error) {
+			mtx_unlock(&sc->lock);
+			SMBUS_CALLBACK(parent, SMB_RELEASE_BUS, &how);
+			return (error);
+		}
 	}
+	mtx_unlock(&sc->lock);
 
 	return (error);
 }
@@ -153,8 +159,8 @@ smbus_request_bus(device_t bus, device_t dev, int how)
 int
 smbus_release_bus(device_t bus, device_t dev)
 {
-	struct smbus_softc *sc = (struct smbus_softc *)device_get_softc(bus);
-	int s, error;
+	struct smbus_softc *sc = device_get_softc(bus);
+	int error;
 
 	/* first, ask the underlying layers if the release is ok */
 	error = SMBUS_CALLBACK(device_get_parent(bus), SMB_RELEASE_BUS, NULL);
@@ -162,17 +168,15 @@ smbus_release_bus(device_t bus, device_t dev)
 	if (error)
 		return (error);
 
-	s = splhigh();
-	if (sc->owner != dev) {
-		splx(s);
-		return (EACCES);
-	}
-
-	sc->owner = 0;
-	splx(s);
+	mtx_lock(&sc->lock);
+	if (sc->owner == dev) {
+		sc->owner = NULL;
 
-	/* wakeup waiting processes */
-	wakeup(sc);
+		/* wakeup waiting processes */
+		wakeup(sc);
+	} else
+		error = EACCES;
+	mtx_unlock(&sc->lock);
 
-	return (0);
+	return (error);
 }
diff --git a/sys/dev/smbus/smbconf.h b/sys/dev/smbus/smbconf.h
index 64b0a33..a3d403d 100644
--- a/sys/dev/smbus/smbconf.h
+++ b/sys/dev/smbus/smbconf.h
@@ -59,6 +59,7 @@
 #define SMB_EABORT	0x10
 #define SMB_ETIMEOUT	0x20
 #define SMB_EBUSY	0x40
+#define	SMB_EINVAL	0x100
 
 /*
  * How Quick command is executed
@@ -69,16 +70,19 @@
 /*
  * ivars codes
  */
-#define SMBUS_IVAR_ADDR	0x1	/* I2C address of the device */
+#define SMBUS_IVAR_ADDR	0x1	/* slave address of the device */
 
-extern int smbus_request_bus(device_t, device_t, int);
-extern int smbus_release_bus(device_t, device_t);
-extern device_t smbus_alloc_bus(device_t);
-extern int smbus_error(int error);
+int	smbus_request_bus(device_t, device_t, int);
+int	smbus_release_bus(device_t, device_t);
+device_t smbus_alloc_bus(device_t);
+int	smbus_error(int error);
 
-extern void smbus_intr(device_t, u_char, char low, char high, int error);
+void	smbus_intr(device_t, u_char, char low, char high, int error);
 
-extern u_char smbus_get_addr(device_t);
+u_char	smbus_get_addr(device_t);
+
+extern driver_t smbus_driver;
+extern devclass_t smbus_devclass;
 
 #define smbus_quick(bus,slave,how) \
 	(SMBUS_QUICK(device_get_parent(bus), slave, how))
diff --git a/sys/dev/smbus/smbus.c b/sys/dev/smbus/smbus.c
index 6a67eb6..ce7bdc6 100644
--- a/sys/dev/smbus/smbus.c
+++ b/sys/dev/smbus/smbus.c
@@ -30,32 +30,30 @@
 __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
-#include <sys/kernel.h>
+#include <sys/lock.h>
 #include <sys/module.h>
+#include <sys/mutex.h>
 #include <sys/bus.h> 
 
 #include <dev/smbus/smbconf.h>
 #include <dev/smbus/smbus.h>
 
 /*
- * Autoconfiguration and support routines for the Philips serial I2C bus
+ * Autoconfiguration and support routines for System Management bus
  */
 
-#define DEVTOSMBUS(dev) ((struct smbus_device*)device_get_ivars(dev))
-
-static devclass_t smbus_devclass;
-
 /*
  * Device methods
  */
 static int smbus_probe(device_t);
 static int smbus_attach(device_t);
+static int smbus_detach(device_t);
 
 static device_method_t smbus_methods[] = {
         /* device interface */
         DEVMETHOD(device_probe,         smbus_probe),
         DEVMETHOD(device_attach,        smbus_attach),
-        DEVMETHOD(device_detach,        bus_generic_detach),
+        DEVMETHOD(device_detach,        smbus_detach),
 
         /* bus interface */
         DEVMETHOD(bus_print_child,	bus_generic_print_child),
@@ -63,12 +61,14 @@ static device_method_t smbus_methods[] = {
         { 0, 0 }
 };
 
-static driver_t smbus_driver = {
+driver_t smbus_driver = {
         "smbus",
         smbus_methods,
         sizeof(struct smbus_softc),
 };
 
+devclass_t smbus_devclass;
+
 /*
  * At 'probe' time, we add all the devices which we know about to the
  * bus.  The generic attach routine will probe and attach them if they
@@ -77,6 +77,7 @@ static driver_t smbus_driver = {
 static int
 smbus_probe(device_t dev)
 {
+
 	device_set_desc(dev, "System Management Bus");
 
 	return (0);
@@ -85,25 +86,32 @@ smbus_probe(device_t dev)
 static int
 smbus_attach(device_t dev)
 {
-	device_add_child(dev, NULL, -1);
+	struct smbus_softc *sc = device_get_softc(dev);
+
+	mtx_init(&sc->lock, device_get_nameunit(dev), "smbus", MTX_DEF);
+	bus_generic_probe(dev);
 	bus_generic_attach(dev);
 
 	return (0);
 }
 
+static int
+smbus_detach(device_t dev)
+{
+	struct smbus_softc *sc = device_get_softc(dev);
+	int error;
+
+	error = bus_generic_detach(dev);
+	if (error)
+		return (error);
+	mtx_destroy(&sc->lock);
+
+	return (0);
+}
+
 void
 smbus_generic_intr(device_t dev, u_char devaddr, char low, char high)
 {
-	return;
 }
 
-DRIVER_MODULE(smbus, iicsmb, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, bktr, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, intsmb, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, alpm, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, ichsmb, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, amdpm, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, amdsmb, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, nfsmb, smbus_driver, smbus_devclass, 0, 0);
-DRIVER_MODULE(smbus, viapropm, smbus_driver, smbus_devclass, 0, 0);
 MODULE_VERSION(smbus, SMBUS_MODVER);
diff --git a/sys/dev/smbus/smbus.h b/sys/dev/smbus/smbus.h
index cd84cc8..f8335e8 100644
--- a/sys/dev/smbus/smbus.h
+++ b/sys/dev/smbus/smbus.h
@@ -30,10 +30,10 @@
 #define __SMBUS_H
 
 struct smbus_softc {
-
 	device_t owner;		/* smbus owner device structure */
+	struct mtx lock;
 };
 
-extern void smbus_generic_intr(device_t dev, u_char devaddr, char low, char high);
+void	smbus_generic_intr(device_t dev, u_char devaddr, char low, char high);
 
 #endif
diff --git a/sys/dev/smbus/smbus_if.m b/sys/dev/smbus/smbus_if.m
index 6b213e1..d969e25 100644
--- a/sys/dev/smbus/smbus_if.m
+++ b/sys/dev/smbus/smbus_if.m
@@ -47,7 +47,7 @@ METHOD void intr {
 METHOD int callback {
 	device_t dev;
 	int index;
-	caddr_t data;
+	void *data;
 };
 
 #
@@ -146,6 +146,6 @@ METHOD int bread {
 	device_t dev;
 	u_char slave;
 	char cmd;
-	u_char count;
+	u_char *count;
 	char *buf;
 };
diff --git a/sys/pci/alpm.c b/sys/pci/alpm.c
index e6f8149..d90d919 100644
--- a/sys/pci/alpm.c
+++ b/sys/pci/alpm.c
@@ -259,7 +259,7 @@ alpm_detach(device_t dev)
 }
 
 static int
-alpm_callback(device_t dev, int index, caddr_t *data)
+alpm_callback(device_t dev, int index, void *data)
 {
 	int error = 0;
 
@@ -525,82 +525,76 @@ static int
 alpm_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 {
 	struct alpm_softc *sc = (struct alpm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char i;
+	int error;
 
+	if (count < 1 || count > 32)
+		return (SMB_EINVAL);
 	alpm_clear(sc);
 	if(!alpm_idle(sc))
 		return (SMB_EBUSY);
 
-	remain = count;
-	while (remain) {
-		len = min(remain, 32);
-
-		ALPM_SMBOUTB(sc, SMBHADDR, slave & ~LSB);
+	ALPM_SMBOUTB(sc, SMBHADDR, slave & ~LSB);
 	
-		/* set the cmd and reset the
-		 * 32-byte long internal buffer */
-		ALPM_SMBOUTB(sc, SMBCMD, SMBWRBLOCK | SMB_BLK_CLR);
-
-		ALPM_SMBOUTB(sc, SMBHDATA, len);
+	/* set the cmd and reset the
+	 * 32-byte long internal buffer */
+	ALPM_SMBOUTB(sc, SMBCMD, SMBWRBLOCK | SMB_BLK_CLR);
 
-		/* fill the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			ALPM_SMBOUTB(sc, SMBHBLOCK, buf[count-remain+i]);
-			DELAY(2);
-		}
-		ALPM_SMBOUTB(sc, SMBHCMD, cmd);
-		ALPM_SMBOUTB(sc, SMBSTART, 0xff);
+	ALPM_SMBOUTB(sc, SMBHDATA, count);
 
-		if ((error = alpm_wait(sc)) != SMB_ENOERR)
-			goto error;
-
-		remain -= len;
+	/* fill the 32-byte internal buffer */
+	for (i = 0; i < count; i++) {
+		ALPM_SMBOUTB(sc, SMBHBLOCK, buf[i]);
+		DELAY(2);
 	}
+	ALPM_SMBOUTB(sc, SMBHCMD, cmd);
+	ALPM_SMBOUTB(sc, SMBSTART, 0xff);
+
+	error = alpm_wait(sc);
 
-error:
 	ALPM_DEBUG(printf("alpm: WRITEBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
 
 	return (error);
 }
 
 static int
-alpm_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+alpm_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	struct alpm_softc *sc = (struct alpm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char data, len, i;
+	int error;
 
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 	alpm_clear(sc);
 	if (!alpm_idle(sc))
 		return (SMB_EBUSY);
 
-	remain = count;
-	while (remain) {
-		ALPM_SMBOUTB(sc, SMBHADDR, slave | LSB);
+	ALPM_SMBOUTB(sc, SMBHADDR, slave | LSB);
 	
-		/* set the cmd and reset the
-		 * 32-byte long internal buffer */
-		ALPM_SMBOUTB(sc, SMBCMD, SMBWRBLOCK | SMB_BLK_CLR);
+	/* set the cmd and reset the
+	 * 32-byte long internal buffer */
+	ALPM_SMBOUTB(sc, SMBCMD, SMBWRBLOCK | SMB_BLK_CLR);
 
-		ALPM_SMBOUTB(sc, SMBHCMD, cmd);
-		ALPM_SMBOUTB(sc, SMBSTART, 0xff);
+	ALPM_SMBOUTB(sc, SMBHCMD, cmd);
+	ALPM_SMBOUTB(sc, SMBSTART, 0xff);
 
-		if ((error = alpm_wait(sc)) != SMB_ENOERR)
+	if ((error = alpm_wait(sc)) != SMB_ENOERR)
 			goto error;
 
-		len = ALPM_SMBINB(sc, SMBHDATA);
+	len = ALPM_SMBINB(sc, SMBHDATA);
 
-		/* read the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			buf[count-remain+i] = ALPM_SMBINB(sc, SMBHBLOCK);
-			DELAY(2);
-		}
-
-		remain -= len;
+	/* read the 32-byte internal buffer */
+	for (i = 0; i < len; i++) {
+		data = ALPM_SMBINB(sc, SMBHBLOCK);
+		if (i < *count)
+			buf[i] = data;
+		DELAY(2);
 	}
+	*count = len;
+
 error:
-	ALPM_DEBUG(printf("alpm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
+	ALPM_DEBUG(printf("alpm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, *count, cmd, error));
 
 	return (error);
 }
@@ -635,6 +629,7 @@ static driver_t alpm_driver = {
 };
 
 DRIVER_MODULE(alpm, pci, alpm_driver, alpm_devclass, 0, 0);
+DRIVER_MODULE(smbus, alpm, smbus_driver, smbus_devclass, 0, 0);
 MODULE_DEPEND(alpm, pci, 1, 1, 1);
 MODULE_DEPEND(alpm, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
 MODULE_VERSION(alpm, 1);
diff --git a/sys/pci/amdpm.c b/sys/pci/amdpm.c
index 841b037..fb34642 100644
--- a/sys/pci/amdpm.c
+++ b/sys/pci/amdpm.c
@@ -236,7 +236,7 @@ amdpm_detach(device_t dev)
 }
 
 static int
-amdpm_callback(device_t dev, int index, caddr_t *data)
+amdpm_callback(device_t dev, int index, void *data)
 {
 	int error = 0;
 
@@ -504,84 +504,79 @@ static int
 amdpm_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 {
 	struct amdpm_softc *sc = (struct amdpm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char i;
+	int error;
 	u_short l;
 
+	if (count < 1 || count > 32)
+		return (SMB_EINVAL);
 	amdpm_clear(sc);
 	if(!amdpm_idle(sc))
 		return (SMB_EBUSY);
 
-	remain = count;
-	while (remain) {
-		len = min(remain, 32);
-
-		AMDPM_SMBOUTW(sc, AMDSMB_HSTADDR, slave & ~LSB);
+	AMDPM_SMBOUTW(sc, AMDSMB_HSTADDR, slave & ~LSB);
 	
-		/*
-		 * Do we have to reset the internal 32-byte buffer?
-		 * Can't see how to do this from the data sheet.
-		 */
-
-		AMDPM_SMBOUTW(sc, AMDSMB_HSTDATA, len);
-
-		/* Fill the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			AMDPM_SMBOUTB(sc, AMDSMB_HSTDFIFO, buf[count-remain+i]);
-			DELAY(2);
-		}
-		AMDPM_SMBOUTB(sc, AMDSMB_HSTCMD, cmd);
-		l = AMDPM_SMBINW(sc, AMDSMB_GLOBAL_ENABLE);
-		AMDPM_SMBOUTW(sc, AMDSMB_GLOBAL_ENABLE, (l & 0xfff8) | AMDSMB_GE_CYC_BLOCK | AMDSMB_GE_HOST_STC);
-
-		if ((error = amdpm_wait(sc)) != SMB_ENOERR)
-			goto error;
-
-		remain -= len;
+	/*
+	 * Do we have to reset the internal 32-byte buffer?
+	 * Can't see how to do this from the data sheet.
+	 */
+	AMDPM_SMBOUTW(sc, AMDSMB_HSTDATA, count);
+
+	/* Fill the 32-byte internal buffer */
+	for (i = 0; i < count; i++) {
+		AMDPM_SMBOUTB(sc, AMDSMB_HSTDFIFO, buf[i]);
+		DELAY(2);
 	}
+	AMDPM_SMBOUTB(sc, AMDSMB_HSTCMD, cmd);
+	l = AMDPM_SMBINW(sc, AMDSMB_GLOBAL_ENABLE);
+	AMDPM_SMBOUTW(sc, AMDSMB_GLOBAL_ENABLE,
+	    (l & 0xfff8) | AMDSMB_GE_CYC_BLOCK | AMDSMB_GE_HOST_STC);
+
+	error = amdpm_wait(sc);
 
-error:
 	AMDPM_DEBUG(printf("amdpm: WRITEBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
 
 	return (error);
 }
 
 static int
-amdpm_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+amdpm_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	struct amdpm_softc *sc = (struct amdpm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char data, len, i;
+	int error;
 	u_short l;
 
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 	amdpm_clear(sc);
 	if (!amdpm_idle(sc))
 		return (SMB_EBUSY);
 
-	remain = count;
-	while (remain) {
-		AMDPM_SMBOUTW(sc, AMDSMB_HSTADDR, slave | LSB);
+	AMDPM_SMBOUTW(sc, AMDSMB_HSTADDR, slave | LSB);
 	
-		AMDPM_SMBOUTB(sc, AMDSMB_HSTCMD, cmd);
+	AMDPM_SMBOUTB(sc, AMDSMB_HSTCMD, cmd);
 
-		l = AMDPM_SMBINW(sc, AMDSMB_GLOBAL_ENABLE);
-		AMDPM_SMBOUTW(sc, AMDSMB_GLOBAL_ENABLE, (l & 0xfff8) | AMDSMB_GE_CYC_BLOCK | AMDSMB_GE_HOST_STC);
+	l = AMDPM_SMBINW(sc, AMDSMB_GLOBAL_ENABLE);
+	AMDPM_SMBOUTW(sc, AMDSMB_GLOBAL_ENABLE,
+	    (l & 0xfff8) | AMDSMB_GE_CYC_BLOCK | AMDSMB_GE_HOST_STC);
 		
-		if ((error = amdpm_wait(sc)) != SMB_ENOERR)
-			goto error;
-
-		len = AMDPM_SMBINW(sc, AMDSMB_HSTDATA);
+	if ((error = amdpm_wait(sc)) != SMB_ENOERR)
+		goto error;
 
-		/* Read the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			buf[count-remain+i] = AMDPM_SMBINB(sc, AMDSMB_HSTDFIFO);
-			DELAY(2);
-		}
+	len = AMDPM_SMBINW(sc, AMDSMB_HSTDATA);
 
-		remain -= len;
+	/* Read the 32-byte internal buffer */
+	for (i = 0; i < len; i++) {
+		data = AMDPM_SMBINB(sc, AMDSMB_HSTDFIFO);
+		if (i < *count)
+			buf[i] = data;
+		DELAY(2);
 	}
+	*count = len;
+
 error:
-	AMDPM_DEBUG(printf("amdpm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
+	AMDPM_DEBUG(printf("amdpm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, *count, cmd, error));
 
 	return (error);
 }
@@ -616,8 +611,8 @@ static driver_t amdpm_driver = {
 };
 
 DRIVER_MODULE(amdpm, pci, amdpm_driver, amdpm_devclass, 0, 0);
+DRIVER_MODULE(smbus, amdpm, smbus_driver, smbus_devclass, 0, 0);
 
 MODULE_DEPEND(amdpm, pci, 1, 1, 1);
 MODULE_DEPEND(amdpm, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
 MODULE_VERSION(amdpm, 1);
-
diff --git a/sys/pci/amdsmb.c b/sys/pci/amdsmb.c
index 60febd5..dde1f12 100644
--- a/sys/pci/amdsmb.c
+++ b/sys/pci/amdsmb.c
@@ -162,7 +162,7 @@ amdsmb_detach(device_t dev)
 }
 
 static int
-amdsmb_callback(device_t dev, int index, caddr_t *data)
+amdsmb_callback(device_t dev, int index, void *data)
 {
 	int error = 0;
 
@@ -444,13 +444,14 @@ static int
 amdsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 {
 	struct amdsmb_softc *sc = (struct amdsmb_softc *)device_get_softc(dev);
-	u_char len, i;
+	u_char i;
 	int error;
 
-	len = min(count, 32);
+	if (count < 1 || count > 32)
+		return (SMB_EINVAL);
 	amdsmb_ec_write(sc, SMB_CMD, cmd);
-	amdsmb_ec_write(sc, SMB_BCNT, len);
-	for (i = 0; i < len; i++)
+	amdsmb_ec_write(sc, SMB_BCNT, count);
+	for (i = 0; i < count; i++)
 		amdsmb_ec_write(sc, SMB_DATA + i, buf[i]);
 	amdsmb_ec_write(sc, SMB_ADDR, slave);
 	amdsmb_ec_write(sc, SMB_PRTCL, SMB_PRTCL_WRITE | SMB_PRTCL_BLOCK_DATA);
@@ -464,25 +465,30 @@ amdsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 }
 
 static int
-amdsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+amdsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	struct amdsmb_softc *sc = (struct amdsmb_softc *)device_get_softc(dev);
-	u_char len, i;
+	u_char data, len, i;
 	int error;
 
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 	amdsmb_ec_write(sc, SMB_CMD, cmd);
 	amdsmb_ec_write(sc, SMB_ADDR, slave);
 	amdsmb_ec_write(sc, SMB_PRTCL, SMB_PRTCL_READ | SMB_PRTCL_BLOCK_DATA);
 
 	if ((error = amdsmb_wait(sc)) == SMB_ENOERR) {
 		amdsmb_ec_read(sc, SMB_BCNT, &len);
-		len = min(len, 32);
-		for (i = 0; i < len; i++)
-			amdsmb_ec_read(sc, SMB_DATA + i, buf + i);
+		for (i = 0; i < len; i++) {
+			amdsmb_ec_read(sc, SMB_DATA + i, &data);
+			if (i < *count)
+				buf[i] = data;
+		}
+		*count = len;
 	}
 
 	AMDSMB_DEBUG(printf("amdsmb: READBLK to 0x%x, count=0x%x, cmd=0x%x, "
-	    "error=0x%x", slave, count, cmd, error));
+	    "error=0x%x", slave, *count, cmd, error));
 
 	return (error);
 }
@@ -517,6 +523,7 @@ static driver_t amdsmb_driver = {
 };
 
 DRIVER_MODULE(amdsmb, pci, amdsmb_driver, amdsmb_devclass, 0, 0);
+DRIVER_MODULE(smbus, amdsmb, smbus_driver, smbus_devclass, 0, 0);
 
 MODULE_DEPEND(amdsmb, pci, 1, 1, 1);
 MODULE_DEPEND(amdsmb, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
diff --git a/sys/pci/intpm.c b/sys/pci/intpm.c
index 1e454bb..3bf1c2c 100644
--- a/sys/pci/intpm.c
+++ b/sys/pci/intpm.c
@@ -71,7 +71,7 @@ static int intsmb_attach(device_t);
 static int intsmb_intr(device_t dev);
 static int intsmb_slvintr(device_t dev);
 static void  intsmb_alrintr(device_t dev);
-static int intsmb_callback(device_t dev, int index, caddr_t data);
+static int intsmb_callback(device_t dev, int index, void *data);
 static int intsmb_quick(device_t dev, u_char slave, int how);
 static int intsmb_sendb(device_t dev, u_char slave, char byte);
 static int intsmb_recvb(device_t dev, u_char slave, char *byte);
@@ -81,7 +81,7 @@ static int intsmb_readb(device_t dev, u_char slave, char cmd, char *byte);
 static int intsmb_readw(device_t dev, u_char slave, char cmd, short *word);
 static int intsmb_pcall(device_t dev, u_char slave, char cmd, short sdata, short *rdata);
 static int intsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf);
-static int intsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf);
+static int intsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf);
 static void intsmb_start(device_t dev,u_char cmd,int nointr);
 static int intsmb_stop(device_t dev);
 static int intsmb_stop_poll(device_t dev);
@@ -175,7 +175,7 @@ intsmb_attach(device_t dev)
 }
 
 static int 
-intsmb_callback(device_t dev, int index, caddr_t data)
+intsmb_callback(device_t dev, int index, void *data)
 {
 	int error = 0;
 	intrmask_t s;
@@ -585,7 +585,7 @@ intsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
         struct intsmb_softc *sc = (struct intsmb_softc *)device_get_softc(dev);
         error=intsmb_free(dev);
         if(count>SMBBLOCKTRANS_MAX||count==0)
-                error=EINVAL;
+                error=SMB_EINVAL;
         if(!error){
                 /*Reset internal array index*/
                 bus_space_read_1(sc->st,sc->sh,PIIX4_SMBHSTCNT);
@@ -603,32 +603,35 @@ intsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 }
 
 static int
-intsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+intsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
         int error,i;
+	u_char data, nread;
         struct intsmb_softc *sc = (struct intsmb_softc *)device_get_softc(dev);
         error=intsmb_free(dev);
-        if(count>SMBBLOCKTRANS_MAX||count==0)
-                error=EINVAL;
+        if(*count>SMBBLOCKTRANS_MAX||*count==0)
+                error=SMB_EINVAL;
         if(!error){
                 /*Reset internal array index*/
                 bus_space_read_1(sc->st,sc->sh,PIIX4_SMBHSTCNT);
 		
                 bus_space_write_1(sc->st,sc->sh,PIIX4_SMBHSTADD,slave|LSB);
                 bus_space_write_1(sc->st,sc->sh,PIIX4_SMBHSTCMD,cmd);
-                bus_space_write_1(sc->st,sc->sh,PIIX4_SMBHSTDAT0,count);
+                bus_space_write_1(sc->st,sc->sh,PIIX4_SMBHSTDAT0,*count);
                 intsmb_start(dev,PIIX4_SMBHSTCNT_PROT_BLOCK,0);
                 error=intsmb_stop(dev);
                 if(!error){
-                        bzero(buf,count);/*Is it needed?*/
-                        count= bus_space_read_1(sc->st,sc->sh,
+                        nread= bus_space_read_1(sc->st,sc->sh,
 						PIIX4_SMBHSTDAT0);
-                        if(count!=0&&count<=SMBBLOCKTRANS_MAX){
-			        for(i=0;i<count;i++){
-				        buf[i]=bus_space_read_1(sc->st,
+                        if(nread!=0&&nread<=SMBBLOCKTRANS_MAX){
+			        for(i=0;i<nread;i++){
+					data = bus_space_read_1(sc->st,
 								sc->sh,
 								PIIX4_SMBBLKDAT);
+					if (i < *count)
+						buf[i] = data;
 				}
+				*count = nread;
 			}
                         else{
 				error=EIO;
@@ -739,6 +742,7 @@ intpm_probe(device_t dev)
     }
 }
 DRIVER_MODULE(intpm, pci , intpm_pci_driver, intpm_devclass, 0, 0);
+DRIVER_MODULE(smbus, intsmb, smbus_driver, smbus_devclass, 0, 0);
 MODULE_DEPEND(intpm, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
 MODULE_VERSION(intpm, 1);
 
diff --git a/sys/pci/nfsmb.c b/sys/pci/nfsmb.c
index 5cd1b08..1511121 100644
--- a/sys/pci/nfsmb.c
+++ b/sys/pci/nfsmb.c
@@ -252,7 +252,7 @@ nfsmb_detach(device_t dev)
 }
 
 static int
-nfsmb_callback(device_t dev, int index, caddr_t *data)
+nfsmb_callback(device_t dev, int index, void *data)
 {
 	int error = 0;
 
@@ -456,13 +456,14 @@ static int
 nfsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 {
 	struct nfsmb_softc *sc = (struct nfsmb_softc *)device_get_softc(dev);
-	u_char len, i;
+	u_char i;
 	int error;
 
-	len = min(count, 32);
+	if (count < 1 || count > 32)
+		return (SMB_EINVAL);
 	NFSMB_SMBOUTB(sc, SMB_CMD, cmd);
-	NFSMB_SMBOUTB(sc, SMB_BCNT, len);
-	for (i = 0; i < len; i++)
+	NFSMB_SMBOUTB(sc, SMB_BCNT, count);
+	for (i = 0; i < count; i++)
 		NFSMB_SMBOUTB(sc, SMB_DATA + i, buf[i]);
 	NFSMB_SMBOUTB(sc, SMB_ADDR, slave);
 	NFSMB_SMBOUTB(sc, SMB_PRTCL, SMB_PRTCL_WRITE | SMB_PRTCL_BLOCK_DATA);
@@ -475,24 +476,29 @@ nfsmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 }
 
 static int
-nfsmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+nfsmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	struct nfsmb_softc *sc = (struct nfsmb_softc *)device_get_softc(dev);
-	u_char len, i;
+	u_char data, len, i;
 	int error;
 
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 	NFSMB_SMBOUTB(sc, SMB_CMD, cmd);
 	NFSMB_SMBOUTB(sc, SMB_ADDR, slave);
 	NFSMB_SMBOUTB(sc, SMB_PRTCL, SMB_PRTCL_READ | SMB_PRTCL_BLOCK_DATA);
 
 	if ((error = nfsmb_wait(sc)) == SMB_ENOERR) {
 		len = NFSMB_SMBINB(sc, SMB_BCNT);
-		len = min(len, 32);
-		for (i = 0; i < len; i++)
-			buf[i] = NFSMB_SMBINB(sc, SMB_DATA + i);
+		for (i = 0; i < len; i++) {
+			data = NFSMB_SMBINB(sc, SMB_DATA + i);
+			if (i < *count)
+				buf[i] = data;
+		}
+		*count = len;
 	}
 
-	NFSMB_DEBUG(printf("nfsmb: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
+	NFSMB_DEBUG(printf("nfsmb: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, *count, cmd, error));
 
 	return (error);
 }
@@ -555,6 +561,7 @@ static driver_t nfsmbsub_driver = {
 
 DRIVER_MODULE(nfsmb, pci, nfsmb_driver, nfsmb_devclass, 0, 0);
 DRIVER_MODULE(nfsmb, nfsmb, nfsmbsub_driver, nfsmb_devclass, 0, 0);
+DRIVER_MODULE(smbus, nfsmb, smbus_driver, smbus_devclass, 0, 0);
 
 MODULE_DEPEND(nfsmb, pci, 1, 1, 1);
 MODULE_DEPEND(nfsmb, smbus, SMBUS_MINVER, SMBUS_PREFVER, SMBUS_MAXVER);
diff --git a/sys/pci/viapm.c b/sys/pci/viapm.c
index 0bddb22..a26703e 100644
--- a/sys/pci/viapm.c
+++ b/sys/pci/viapm.c
@@ -640,7 +640,7 @@ viasmb_quick(device_t dev, u_char slave, int how)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	switch (how) {
 	case SMB_QWRITE:
@@ -670,7 +670,7 @@ viasmb_sendb(device_t dev, u_char slave, char byte)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave & ~ LSB);
 	VIAPM_OUTB(SMBHCMD, byte);
@@ -692,7 +692,7 @@ viasmb_recvb(device_t dev, u_char slave, char *byte)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave | LSB);
 
@@ -714,7 +714,7 @@ viasmb_writeb(device_t dev, u_char slave, char cmd, char byte)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave & ~ LSB);
 	VIAPM_OUTB(SMBHCMD, cmd);
@@ -737,7 +737,7 @@ viasmb_readb(device_t dev, u_char slave, char cmd, char *byte)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave | LSB);
 	VIAPM_OUTB(SMBHCMD, cmd);
@@ -760,7 +760,7 @@ viasmb_writew(device_t dev, u_char slave, char cmd, short word)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave & ~ LSB);
 	VIAPM_OUTB(SMBHCMD, cmd);
@@ -785,7 +785,7 @@ viasmb_readw(device_t dev, u_char slave, char cmd, short *word)
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
+		return (SMB_EBUSY);
 
 	VIAPM_OUTB(SMBHADDR, slave | LSB);
 	VIAPM_OUTB(SMBHCMD, cmd);
@@ -808,37 +808,31 @@ static int
 viasmb_bwrite(device_t dev, u_char slave, char cmd, u_char count, char *buf)
 {
 	struct viapm_softc *viapm = (struct viapm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char i;
+	int error;
+
+	if (count < 1 || count > 32)
+		return (SMB_EINVAL);
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
-
-	remain = count;
-	while (remain) {
-		len = min(remain, 32);
-
-		VIAPM_OUTB(SMBHADDR, slave & ~LSB);
-		VIAPM_OUTB(SMBHCMD, cmd);
-		VIAPM_OUTB(SMBHDATA0, len);
-		i = VIAPM_INB(SMBHCTRL);
-
-		/* fill the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			VIAPM_OUTB(SMBHBLOCK, buf[count-remain+i]);
-			DELAY(2);
-		}
-		VIAPM_OUTB(SMBHCMD, cmd);
-		VIAPM_OUTB(SMBHCTRL, SMBHCTRL_START | SMBHCTRL_BLOCK);
+		return (SMB_EBUSY);
 
-		if ((error = viapm_wait(viapm)) != SMB_ENOERR)
-			goto error;
+	VIAPM_OUTB(SMBHADDR, slave & ~LSB);
+	VIAPM_OUTB(SMBHCMD, cmd);
+	VIAPM_OUTB(SMBHDATA0, count);
+	i = VIAPM_INB(SMBHCTRL);
 
-		remain -= len;
+	/* fill the 32-byte internal buffer */
+	for (i = 0; i < count; i++) {
+		VIAPM_OUTB(SMBHBLOCK, buf[i]);
+		DELAY(2);
 	}
+	VIAPM_OUTB(SMBHCMD, cmd);
+	VIAPM_OUTB(SMBHCTRL, SMBHCTRL_START | SMBHCTRL_BLOCK);
+
+	error = viapm_wait(viapm);
 
-error:
 	VIAPM_DEBUG(printf("viapm: WRITEBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
 
 	return (error);
@@ -846,40 +840,40 @@ error:
 }
 
 static int
-viasmb_bread(device_t dev, u_char slave, char cmd, u_char count, char *buf)
+viasmb_bread(device_t dev, u_char slave, char cmd, u_char *count, char *buf)
 {
 	struct viapm_softc *viapm = (struct viapm_softc *)device_get_softc(dev);
-	u_char remain, len, i;
-	int error = SMB_ENOERR;
+	u_char data, len, i;
+	int error;
+
+	if (*count < 1 || *count > 32)
+		return (SMB_EINVAL);
 
 	viapm_clear(viapm);
 	if (viapm_busy(viapm))
-		return (EBUSY);
-
-	remain = count;
-	while (remain) {
-		VIAPM_OUTB(SMBHADDR, slave | LSB);
-		VIAPM_OUTB(SMBHCMD, cmd);
-		VIAPM_OUTB(SMBHCTRL, SMBHCTRL_START | SMBHCTRL_BLOCK);
-
-		if ((error = viapm_wait(viapm)) != SMB_ENOERR)
-			goto error;
+		return (SMB_EBUSY);
 
-		len = VIAPM_INB(SMBHDATA0);
-		i = VIAPM_INB(SMBHCTRL); 		/* reset counter */
+	VIAPM_OUTB(SMBHADDR, slave | LSB);
+	VIAPM_OUTB(SMBHCMD, cmd);
+	VIAPM_OUTB(SMBHCTRL, SMBHCTRL_START | SMBHCTRL_BLOCK);
 
-		len = min(len, remain);
+	if ((error = viapm_wait(viapm)) != SMB_ENOERR)
+		goto error;
 
-		/* read the 32-byte internal buffer */
-		for (i=0; i<len; i++) {
-			buf[count-remain+i] = VIAPM_INB(SMBHBLOCK);
-			DELAY(2);
-		}
+	len = VIAPM_INB(SMBHDATA0);
+	i = VIAPM_INB(SMBHCTRL); 		/* reset counter */
 
-		remain -= len;
+	/* read the 32-byte internal buffer */
+	for (i = 0; i < len; i++) {
+		data = VIAPM_INB(SMBHBLOCK);
+		if (i < *count)
+			buf[i] = data;
+		DELAY(2);
 	}
+	*count = len;
+
 error:
-	VIAPM_DEBUG(printf("viapm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, count, cmd, error));
+	VIAPM_DEBUG(printf("viapm: READBLK to 0x%x, count=0x%x, cmd=0x%x, error=0x%x", slave, *count, cmd, error));
 
 	return (error);
 }
@@ -954,6 +948,7 @@ static driver_t viapropm_driver = {
 
 DRIVER_MODULE(viapm, pci, viapm_driver, viapm_devclass, 0, 0);
 DRIVER_MODULE(viapropm, pci, viapropm_driver, viapropm_devclass, 0, 0);
+DRIVER_MODULE(smbus, viapropm, smbus_driver, smbus_devclass, 0, 0);
 
 MODULE_DEPEND(viapm, pci, 1, 1, 1);
 MODULE_DEPEND(viapropm, pci, 1, 1, 1);