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Date:   Mon, 11 Dec 2017 15:56:14 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>, Peter Rosin <peda@...ntia.se>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] i2c: core: improve return value handling of
 i2c_new_device and i2c_new_dummy

2017-12-06 22:13 GMT+01:00 Heiner Kallweit <hkallweit1@...il.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 compatibilty 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@...il.com>
> ---
>  drivers/i2c/i2c-core-base.c | 46 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 33 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index bb34a5d41..3faa9b1d3 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -656,7 +656,7 @@ static int i2c_dev_irq_from_resources(const struct resource *resources,
>  }
>
>  /**
> - * i2c_new_device - instantiate an i2c device
> + * _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
> @@ -669,17 +669,17 @@ 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 indicate an error.
>   */
> -struct i2c_client *
> -i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
> +static struct i2c_client *
> +_i2c_new_device(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;
>
> @@ -746,7 +746,17 @@ 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);
> +}
> +
> +/* wrapper to be compatible with the current API */
> +struct i2c_client *
> +i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
> +{
> +       struct i2c_client *ret;
> +
> +       ret = _i2c_new_device(adap, info);
> +       return IS_ERR(ret) ? NULL : ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_new_device);
>
> @@ -793,7 +803,7 @@ static struct i2c_driver dummy_driver = {
>  };
>
>  /**
> - * i2c_new_dummy - return a new i2c device bound to a dummy driver
> + * _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
> @@ -808,15 +818,25 @@ 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 indicate an error.
>   */
> -struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
> +static struct i2c_client *
> +_i2c_new_dummy(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(adapter, &info);
> +}
> +
> +/* wrapper to be compatible with the current API */
> +struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
> +{
> +       struct i2c_client *ret;
> +
> +       ret = _i2c_new_dummy(adapter, address);
> +       return IS_ERR(ret) ? NULL : ret;
>  }
>  EXPORT_SYMBOL_GPL(i2c_new_dummy);
>
> @@ -939,9 +959,9 @@ 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(adap, &info);
> +       if (IS_ERR(client))
> +               return PTR_ERR(client);
>
>         /* Keep track of the added device */
>         mutex_lock(&adap->userspace_clients_lock);
> --
> 2.15.1
>
>

Looks good to me in general. I would just rename _i2c_new_device to
__i2c_new_device (with two leading underscores) as it seems to be a
consistent pattern for this kind of private functions in i2c core.

Thanks,
Bartosz

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