[PATCH v2 2/3] i2c: Add helper to ease DMA handling

[Jun Gao <jun.gao-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

From: Jun Gao <jun.gao-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>

This function is needed by i2c_get_dma_safe_msg_buf() potentially.
It is used to free DMA safe buffer when DMA operation fails.

Signed-off-by: Jun Gao <jun.gao-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
---
 drivers/i2c/i2c-core-base.c | 14 ++++++++++++++
 include/linux/i2c.h         |  1 +
 2 files changed, 15 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 31d16ad..2b518ea 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2288,6 +2288,20 @@ void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf)
 }
 EXPORT_SYMBOL_GPL(i2c_release_dma_safe_msg_buf);
 
+/**
+ * i2c_free_dma_safe_msg_buf - free DMA safe buffer
+ * @msg: the message related to DMA safe buffer
+ * @buf: the buffer obtained from i2c_get_dma_safe_msg_buf(). May be NULL.
+ */
+void i2c_free_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf)
+{
+	if (!buf || buf == msg->buf)
+		return;
+
+	kfree(buf);
+}
+EXPORT_SYMBOL_GPL(i2c_free_dma_safe_msg_buf);
+
 MODULE_AUTHOR("Simon G. Vogl <simon-nD9nYVNVf00W+b/DJNNodF6hYfS7NtTn@public.gmane.org>");
 MODULE_DESCRIPTION("I2C-Bus main module");
 MODULE_LICENSE("GPL");
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 254cd34..6d62f93 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -860,6 +860,7 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg)
 
 u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold);
 void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf);
+void i2c_free_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf);
 
 int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr);
 /**
-- 
1.8.1.1