linux-kernel - Re: [PATCH 1/1] mfd: twl4030: clarify the return value for read and write

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Message-ID: <20091207135309.GA23829@esdhcp037198.research.nokia.com>
Date:	Mon, 7 Dec 2009 15:53:09 +0200
From:	Eduardo Valentin <eduardo.valentin@...ia.com>
To:	ext Amit Kucheria <amit.kucheria@...durent.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	"gadiyar@...com" <gadiyar@...com>,
	List Linux Kernel <linux-kernel@...r.kernel.org>,
	List Linux Omap <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 1/1] mfd: twl4030: clarify the return value for read
 and write

On Mon, Dec 07, 2009 at 01:17:29PM +0100, ext Amit Kucheria wrote:
> Infact, we can just return -EIO so that caller knows for sure that all
> messages were not tranferred. Please consider fixed patch instead.
> 
> We should be checking if all the messages were tranferred or not. And return
> -1 for failure. Currently we return success (0) even if none of messages were
> transferred successfully.
> 
> Signed-off-by: Amit Kucheria <amit.kucheria@...durent.com>
> ---
>  drivers/mfd/twl4030-core.c |   24 ++++++++++++++++--------
>  1 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mfd/twl4030-core.c b/drivers/mfd/twl4030-core.c
> index 56f1de5..3d2c413 100644
> --- a/drivers/mfd/twl4030-core.c
> +++ b/drivers/mfd/twl4030-core.c
> @@ -292,10 +292,14 @@ int twl4030_i2c_write(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes)
>  	ret = i2c_transfer(twl->client->adapter, twl->xfer_msg, 1);
>  	mutex_unlock(&twl->xfer_lock);
>  
> -	/* i2cTransfer returns num messages.translate it pls.. */
> -	if (ret >= 0)
> -		ret = 0;
> -	return ret;
> +	/* i2c_transfer returns number of messages transferred */
> +	if (ret != 1) {
> +		pr_err("%s: i2c_write failed to transfer all messages\n",
> +			DRIVER_NAME);
> +		return -EIO;

How about reporting the actual error that has occurred and reported by i2c_transfer?
Instead of just masking it as EIO? If i2c_transfer returns something > 0 then EIO should be right.
But if returns and error code, then that error code must be reported to upper layers.

> +	} else {
> +		return 0;
> +	}
>  }
>  EXPORT_SYMBOL(twl4030_i2c_write);
>  
> @@ -344,10 +348,14 @@ int twl4030_i2c_read(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes)
>  	ret = i2c_transfer(twl->client->adapter, twl->xfer_msg, 2);
>  	mutex_unlock(&twl->xfer_lock);
>  
> -	/* i2cTransfer returns num messages.translate it pls.. */
> -	if (ret >= 0)
> -		ret = 0;
> -	return ret;
> +	/* i2c_transfer returns number of messages transferred */
> +	if (ret != 2) {
> +		pr_err("%s: i2c_read failed to transfer all messages\n",
> +			DRIVER_NAME);
> +		return -EIO;


dito.

> +	} else {
> +		return 0;
> +	}
>  }
>  EXPORT_SYMBOL(twl4030_i2c_read);
>  
> -- 
> 1.6.3.3
> 
> --
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-- 
Eduardo Valentin
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