From 6e1c6c6f92ae9dbb55ebdb1d11907f9fcb540329 Mon Sep 17 00:00:00 2001
From: ian <ian@FreeBSD.org>
Date: Sun, 24 Jan 2016 18:54:11 +0000
Subject: [PATCH] MFC r289726:

  Add iicbus_transfer_excl(), a helper routine to do an i2c bus transaction
  while holding exclusive ownership of the bus.  This is the routine most
  slave drivers should use unless they have a need to acquire and hold the
  bus across a series of related operations that involves multiple transfers.
---
 sys/dev/iicbus/iiconf.c | 15 +++++++++++++++
 sys/dev/iicbus/iiconf.h |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/sys/dev/iicbus/iiconf.c b/sys/dev/iicbus/iiconf.c
index e28d341f8eef..8ac8a47c2edd 100644
--- a/sys/dev/iicbus/iiconf.c
+++ b/sys/dev/iicbus/iiconf.c
@@ -395,6 +395,21 @@ iicbus_transfer(device_t bus, struct iic_msg *msgs, uint32_t nmsgs)
 	return (IICBUS_TRANSFER(device_get_parent(bus), msgs, nmsgs));
 }
 
+int
+iicbus_transfer_excl(device_t dev, struct iic_msg *msgs, uint32_t nmsgs,
+    int how)
+{
+	device_t bus;
+	int error;
+
+	bus = device_get_parent(dev);
+	error = iicbus_request_bus(bus, dev, how);
+	if (error == 0)
+		error = IICBUS_TRANSFER(bus, msgs, nmsgs);
+	iicbus_release_bus(bus, dev);
+	return (error);
+}
+
 /*
  * Generic version of iicbus_transfer that calls the appropriate
  * routines to accomplish this.  See note above about acceptable
diff --git a/sys/dev/iicbus/iiconf.h b/sys/dev/iicbus/iiconf.h
index aca0137d7ea0..12ac0d77319d 100644
--- a/sys/dev/iicbus/iiconf.h
+++ b/sys/dev/iicbus/iiconf.h
@@ -129,6 +129,8 @@ extern int iicbus_block_read(device_t, u_char, char *, int, int *);
 
 /* vectors of iic operations to pass to bridge */
 int iicbus_transfer(device_t bus, struct iic_msg *msgs, uint32_t nmsgs);
+int iicbus_transfer_excl(device_t bus, struct iic_msg *msgs, uint32_t nmsgs,
+    int how);
 int iicbus_transfer_gen(device_t bus, struct iic_msg *msgs, uint32_t nmsgs);
 
 #define IICBUS_MODVER	1