2017-12-15 18:44 GMT+01:00 Heiner Kallweit <hkallweit1@xxxxxxxxx>:
> i2c_new_dummy is typically called from the probe function of the
> driver for the primary i2c client. It requires calls to
> i2c_unregister_device in the error path of the probe function and
> in the remove function.
> This can be simplified by introducing a device-managed version.
>
> Note the changed error case return value type:
> i2c_new_dummy returns NULL whilst devm_new_i2c_dummy returns an ERR_PTR.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Reviewed-by: Bartosz Golaszewski <brgl@xxxxxxxx>
> ---
> v2:
> - use new function _i2c_new_dummy with detailed error codes
> v3:
> - no changes
> v4:
> - reflect renaming to __i2c_new_dummy
> - add reviewed-by
> ---
> Documentation/driver-model/devres.txt | 3 +++
> drivers/i2c/i2c-core-base.c | 38 +++++++++++++++++++++++++++++++++++
> include/linux/i2c.h | 3 +++
> 3 files changed, 44 insertions(+)
>
> diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
> index c180045eb..6e2bccf85 100644
> --- a/Documentation/driver-model/devres.txt
> +++ b/Documentation/driver-model/devres.txt
> @@ -259,6 +259,9 @@ GPIO
> devm_gpio_request_one()
> devm_gpio_free()
>
> +I2C
> + devm_i2c_new_dummy
> +
> IIO
> devm_iio_device_alloc()
> devm_iio_device_free()
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 3b962456c..7a6669f07 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -864,6 +864,44 @@ struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
> }
> EXPORT_SYMBOL_GPL(i2c_new_dummy);
>
> +static void devm_i2c_release_dummy(struct device *dev, void *res)
> +{
> + i2c_unregister_device(*(struct i2c_client **)res);
> +}
> +
> +/**
> + * devm_i2c_new_dummy - return a new i2c device bound to a dummy driver
> + * @dev: device the managed resource is bound to
> + * @adapter: the adapter managing the device
> + * @address: seven bit address to be used
> + * Context: can sleep
> + *
> + * This is the device-managed version of i2c_new_dummy.
> + * Note the changed return value type: It returns the new i2c client
> + * or an ERR_PTR in case of an error.
> + */
> +struct i2c_client *devm_i2c_new_dummy(struct device *dev,
> + struct i2c_adapter *adapter,
> + u16 address)
> +{
> + struct i2c_client *ret, **dr;
> +
> + dr = devres_alloc(devm_i2c_release_dummy, sizeof(*dr), GFP_KERNEL);
> + if (!dr)
> + return ERR_PTR(-ENOMEM);
> +
While I understand that this pattern has been used before I still
think it's much less readable than using a separate devm struct
containing the i2c_client. Please take a look at kernel/irq/irq_sim.c:
while I may be biased since I added that code, I think it's cleaner to
avoid the casts and double pointers. Remember - we prefer readability
over saving three lines of code (and probably none in its compiled
form).
Thanks,
Bartosz
> + ret = __i2c_new_dummy(adapter, address);
> + if (IS_ERR(ret)) {
> + devres_free(dr);
> + } else {
> + *dr = ret;
> + devres_add(dev, dr);
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(devm_i2c_new_dummy);
> +
> /**
> * i2c_new_secondary_device - Helper to get the instantiated secondary address
> * and create the associated device
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 5d7f3c185..aca6ebbb8 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -441,6 +441,9 @@ extern int i2c_probe_func_quick_read(struct i2c_adapter *, unsigned short addr);
> extern struct i2c_client *
> i2c_new_dummy(struct i2c_adapter *adap, u16 address);
>
> +extern struct i2c_client *
> +devm_i2c_new_dummy(struct device *dev, struct i2c_adapter *adap, u16 address);
> +
> extern struct i2c_client *
> i2c_new_secondary_device(struct i2c_client *client,
> const char *name,
> --
> 2.15.1
>
>
