Re: [PATCH v7 1/3] i2c: core: improve return value handling of i2c_new_device and i2c_new_dummy

[Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>]

Hi Wolfram,

On 13/03/2019 16:55, Wolfram Sang wrote:
> From: Heiner Kallweit <hkallweit1@gmail.com>
> 
> Currently i2c_new_device and i2c_new_dummy return just NULL in error
> case although they have more error details internally. Therefore move
> the functionality into new functions returning detailed errors and
> add wrappers for compatibility with the current API.
> 
> This allows to use these functions with detailed error codes within
> the i2c core or for API extensions.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> [wsa: rename new functions to 'errptr' style and fix minor kdoc issues]
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>


As mentioned in 2/3, the _errptr suffix here feels a bit
'hungarian-notation', but I can see how we would want a good clear
distinction between the two types, otherwise we might see people adding
code that checks for ERR_PTR() using the non-errptr functions.

Perhaps that's not really an issue if it's caught by review, or
coccinelle though.


Aside from the function-name-bike-shedding which can be handled as you
wished/discussed in 2/3, and one small grammatical fix in a comment below:


Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>



> ---
>  drivers/i2c/i2c-core-base.c | 70 ++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 57 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index cb6c5cb0df0b..bbca2e8bb019 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -710,7 +710,7 @@ static int i2c_dev_irq_from_resources(const struct resource *resources,
>  }
>  
>  /**
> - * i2c_new_device - instantiate an i2c device
> + * i2c_new_device_errptr - instantiate an i2c device
>   * @adap: the adapter managing the device
>   * @info: describes one I2C device; bus_num is ignored
>   * Context: can sleep
> @@ -723,17 +723,17 @@ static int i2c_dev_irq_from_resources(const struct resource *resources,
>   * before any i2c_adapter could exist.
>   *
>   * This returns the new i2c client, which may be saved for later use with
> - * i2c_unregister_device(); or NULL to indicate an error.
> + * i2c_unregister_device(); or an ERR_PTR to describe the error.
>   */
> -struct i2c_client *
> -i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
> +static struct i2c_client *
> +i2c_new_device_errptr(struct i2c_adapter *adap, struct i2c_board_info const *info)
>  {
>  	struct i2c_client	*client;
>  	int			status;
>  
>  	client = kzalloc(sizeof *client, GFP_KERNEL);
>  	if (!client)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>  
>  	client->adapter = adap;
>  
> @@ -799,7 +799,29 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
>  		client->name, client->addr, status);
>  out_err_silent:
>  	kfree(client);
> -	return NULL;
> +	return ERR_PTR(status);
> +}
> +
> +/**
> + * i2c_new_device - instantiate an i2c device
> + * @adap: the adapter managing the device
> + * @info: describes one I2C device; bus_num is ignored
> + * Context: can sleep
> + *
> + * This function has the same functionality like i2c_new_device_errptr, it just

s/like/as/


> + * returns NULL instead of an ERR_PTR in case of an error for compatibility
> + * with current I2C API.
> + *
> + * This returns the new i2c client, which may be saved for later use with
> + * i2c_unregister_device(); or NULL to indicate an error.
> + */
> +struct i2c_client *
> +i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
> +{
> +	struct i2c_client *ret;
> +
> +	ret = i2c_new_device_errptr(adap, info);
> +	return IS_ERR(ret) ? NULL : ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_new_device);
>  
> @@ -850,7 +872,7 @@ static struct i2c_driver dummy_driver = {
>  };
>  
>  /**
> - * i2c_new_dummy - return a new i2c device bound to a dummy driver
> + * i2c_new_dummy_errptr - return a new i2c device bound to a dummy driver
>   * @adapter: the adapter managing the device
>   * @address: seven bit address to be used
>   * Context: can sleep
> @@ -865,15 +887,37 @@ static struct i2c_driver dummy_driver = {
>   * different driver.
>   *
>   * This returns the new i2c client, which should be saved for later use with
> - * i2c_unregister_device(); or NULL to indicate an error.
> + * i2c_unregister_device(); or an ERR_PTR to describe the error.
>   */
> -struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
> +static struct i2c_client *
> +i2c_new_dummy_errptr(struct i2c_adapter *adapter, u16 address)
>  {
>  	struct i2c_board_info info = {
>  		I2C_BOARD_INFO("dummy", address),
>  	};
>  
> -	return i2c_new_device(adapter, &info);
> +	return i2c_new_device_errptr(adapter, &info);
> +}
> +
> +/**
> + * i2c_new_dummy - return a new i2c device bound to a dummy driver
> + * @adapter: the adapter managing the device
> + * @address: seven bit address to be used
> + * Context: can sleep
> + *
> + * This function has the same functionality like i2c_new_dummy_errptr, it just
> + * returns NULL instead of an ERR_PTR in case of an error for compatibility
> + * with current I2C API.
> + *
> + * This returns the new i2c client, which should be saved for later use with
> + * i2c_unregister_device(); or NULL to indicate an error.
> + */
> +struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
> +{
> +	struct i2c_client *ret;
> +
> +	ret = i2c_new_dummy_errptr(adapter, address);
> +	return IS_ERR(ret) ? NULL : ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_new_dummy);
>  
> @@ -996,9 +1040,9 @@ i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
>  		info.flags |= I2C_CLIENT_SLAVE;
>  	}
>  
> -	client = i2c_new_device(adap, &info);
> -	if (!client)
> -		return -EINVAL;
> +	client = i2c_new_device_errptr(adap, &info);
> +	if (IS_ERR(client))
> +		return PTR_ERR(client);
>  
>  	/* Keep track of the added device */
>  	mutex_lock(&adap->userspace_clients_lock);
>