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

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

[Jean Delvare]

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

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

[Andi Shyti]

Hi Jean,

On Fri, May 31, 2024 at 11:34:07AM +0200, Jean Delvare wrote:
> 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>

Looks good to me:

Reviewed-by: Andi Shyti <andi.shyti@kernel.org>

Thanks,
Andi

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

[Wolfram Sang]

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On Fri, May 31, 2024 at 11:34:07AM GMT, Jean Delvare wrote:
> 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>

Applied to for-next, thanks!


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