Many i2c users consider short transfers to be an error and would prefer
getting -EIO instead of a positive return value and having to convert
it to error code by themselves. So let's add the following new helpers:
i2c_master_send_exact()
i2c_master_recv_exact()
i2c_transfer_exact()
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
Resending to Wolfram's new address...
drivers/i2c/i2c-core.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/i2c.h | 11 ++++++++
2 files changed, 80 insertions(+)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index e388590..6cddb5d 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1430,6 +1430,33 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
EXPORT_SYMBOL(i2c_transfer);
/**
+ * i2c_transfer_exact - transfer given number of I2C messages
+ * @adap: Handle to I2C bus
+ * @msgs: One or more messages to execute before STOP is issued to
+ * terminate the operation; each message begins with a START.
+ * @num: Number of messages to be executed.
+ *
+ * Returns negative errno (including -EIO on short transfer),
+ * or 0 if all messages have been tranferred successfully.
+ *
+ * Note that there is no requirement that each message be sent to
+ * the same slave address, although that is the most common model.
+ */
+int i2c_transfer_exact(struct i2c_adapter *adap,
+ struct i2c_msg *msgs, int num)
+{
+ int ret;
+
+ ret = i2c_transfer(adap, msgs, num);
+ if (ret == num)
+ return 0;
+
+ return ret < 0 ? ret : -EIO;
+
+}
+EXPORT_SYMBOL(i2c_transfer_exact);
+
+/**
* i2c_master_send - issue a single I2C message in master transmit mode
* @client: Handle to slave device
* @buf: Data that will be written to the slave
@@ -1459,6 +1486,27 @@ int i2c_master_send(const struct i2c_client *client, const char *buf, int count)
EXPORT_SYMBOL(i2c_master_send);
/**
+ * i2c_master_send_exact - send exact number of bytes in master transmit mode
+ * @client: Handle to slave device
+ * @buf: Data that will be written to the slave
+ * @count: How many bytes to write, must be less than 64k since msg.len is u16
+ *
+ * Returns negative errno (including -EIO on short transfer), or 0.
+ */
+int i2c_master_send_exact(const struct i2c_client *client,
+ const char *buf, int count)
+{
+ int ret;
+
+ ret = i2c_master_send(client, buf, count);
+ if (ret == count)
+ return 0;
+
+ return ret < 0 ? ret : -EIO;
+}
+EXPORT_SYMBOL(i2c_master_send_exact);
+
+/**
* i2c_master_recv - issue a single I2C message in master receive mode
* @client: Handle to slave device
* @buf: Where to store data read from slave
@@ -1488,6 +1536,27 @@ int i2c_master_recv(const struct i2c_client *client, char *buf, int count)
}
EXPORT_SYMBOL(i2c_master_recv);
+/**
+ * i2c_master_recv_exact - read exact number of bytes in master receive mode
+ * @client: Handle to slave device
+ * @buf: Where to store data read from slave
+ * @count: How many bytes to read, must be less than 64k since msg.len is u16
+ *
+ * Returns negative errno (including -EIO on short transfer), or 0.
+ */
+int i2c_master_recv_exact(const struct i2c_client *client,
+ char *buf, int count)
+{
+ int ret;
+
+ ret = i2c_master_recv(client, buf, count);
+ if (ret == count)
+ return 0;
+
+ return ret < 0 ? ret : -EIO;
+}
+EXPORT_SYMBOL(i2c_master_recv_exact);
+
/* ----------------------------------------------------
* the i2c address scanning function
* Will not work for 10-bit addresses!
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index d0c4db7..3d76059 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -59,13 +59,24 @@ struct module;
*/
extern int i2c_master_send(const struct i2c_client *client, const char *buf,
int count);
+
+extern int i2c_master_send_exact(const struct i2c_client *client,
+ const char *buf, int count);
+
extern int i2c_master_recv(const struct i2c_client *client, char *buf,
int count);
+extern int i2c_master_recv_exact(const struct i2c_client *client,
+ char *buf, int count);
+
/* Transfer num messages.
*/
extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num);
+
+extern int i2c_transfer_exact(struct i2c_adapter *adap,
+ struct i2c_msg *msgs, int num);
+
/* Unlocked flavor */
extern int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int num);
--
Dmitry
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