[PATCH] i2c: dev: Check for I2C_FUNC_I2C before calling i2c_transfer

[Jean Delvare <jdelvare@suse.de>]

It is good practice to check that the underlying adapter supports
I2C transfers before attempting them. The i2c core would eventually
return an error, but it's more efficient to fail early.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
---
Not sure about that one, opinions welcome.

 drivers/i2c/i2c-dev.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- linux-6.9.orig/drivers/i2c/i2c-dev.c
+++ linux-6.9/drivers/i2c/i2c-dev.c
@@ -139,6 +139,10 @@ static ssize_t i2cdev_read(struct file *
 
 	struct i2c_client *client = file->private_data;
 
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
 	if (count > 8192)
 		count = 8192;
 
@@ -163,6 +167,10 @@ static ssize_t i2cdev_write(struct file
 	char *tmp;
 	struct i2c_client *client = file->private_data;
 
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
 	if (count > 8192)
 		count = 8192;
 
@@ -238,6 +246,10 @@ static noinline int i2cdev_ioctl_rdwr(st
 	u8 __user **data_ptrs;
 	int i, res;
 
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
 	data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
 	if (data_ptrs == NULL) {
 		kfree(msgs);


-- 
Jean Delvare
SUSE L3 Support