linux-kernel - Re: [PATCH v2] rtc: abx80x: Fix return value of nvmem callback on read

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Date: Thu, 13 Jun 2024 11:11:02 -0400
From: Sean Anderson <sean.anderson@...o.com>
To: Joy Chakraborty <joychakr@...gle.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
 Dan Carpenter <dan.carpenter@...aro.org>
Cc: linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] rtc: abx80x: Fix return value of nvmem callback on
 read

On 6/13/24 08:07, Joy Chakraborty wrote:
> Read callbacks registered with nvmem core expect 0 to be returned on
> success and a negative value to be returned on failure.
> 
> abx80x_nvmem_xfer() on read calls i2c_smbus_read_i2c_block_data() which
> returns the number of bytes read on success as per its api description,
> this return value is handled as an error and returned to nvmem even on
> success.

Humm, I wish this were documented in nvmem-provider.h...

> Fix to handle all possible values that would be returned by
> i2c_smbus_read_i2c_block_data().
> 
> Fixes: e90ff8ede777 ("rtc: abx80x: Add nvmem support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Joy Chakraborty <joychakr@...gle.com>
> ---
>  drivers/rtc/rtc-abx80x.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
> index fde2b8054c2e..1298962402ff 100644
> --- a/drivers/rtc/rtc-abx80x.c
> +++ b/drivers/rtc/rtc-abx80x.c
> @@ -705,14 +705,18 @@ static int abx80x_nvmem_xfer(struct abx80x_priv *priv, unsigned int offset,
>  		if (ret)
>  			return ret;
>  
> -		if (write)
> +		if (write) {
>  			ret = i2c_smbus_write_i2c_block_data(priv->client, reg,
>  							     len, val);
> -		else
> +			if (ret)
> +				return ret;
> +		} else {
>  			ret = i2c_smbus_read_i2c_block_data(priv->client, reg,
>  							    len, val);
> -		if (ret)
> -			return ret;
> +			if (ret <= 0)
> +				return ret ? ret : -EIO;
> +			len = ret;
> +		}
>  
>  		offset += len;
>  		val += len;

Reviewed-by: Sean Anderson <sean.anderson@...o.com>