[PATCH 0/2] i2c: introduce devm_i2c_new_dummy and use it in at24 driver

[PATCH 0/2] i2c: introduce devm_i2c_new_dummy and use it in at24 driver

[Heiner Kallweit]

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.

Make at24 driver the first user of the new function.

Patch 1 has been submitted and reviewed some time ago, however it
was waiting for a first user until now.

Heiner Kallweit (2):
  i2c: core: add device-managed version of i2c_new_dummy
  eeprom: at24: switch to device-managed version of i2c_new_dummy

 Documentation/driver-model/devres.txt |  3 +++
 drivers/i2c/i2c-core-base.c           | 39 +++++++++++++++++++++++++++++++++++
 drivers/misc/eeprom/at24.c            |  7 +------
 include/linux/i2c.h                   |  3 +++
 4 files changed, 46 insertions(+), 6 deletions(-)

-- 
2.15.1

[PATCH resubmit 1/2] i2c: core: add device-managed version of i2c_new_dummy

[Heiner Kallweit]

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@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
---
 Documentation/driver-model/devres.txt |  3 +++
 drivers/i2c/i2c-core-base.c           | 39 +++++++++++++++++++++++++++++++++++
 include/linux/i2c.h                   |  3 +++
 3 files changed, 45 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 bf52cca87..c1db67f9a 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -820,6 +820,45 @@ 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);
+
+	ret = i2c_new_dummy(adapter, address);
+	if (!ret) {
+		devres_free(dr);
+		return ERR_PTR(-EBUSY);
+	}
+
+	*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 a556db976..c27eac1e1 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -383,6 +383,9 @@ 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

[PATCH resubmit 2/2] eeprom: at24: switch to device-managed version of i2c_new_dummy

[Heiner Kallweit]

Make use of recently introduced device-managed version of
i2c_new_dummy to simplify the code.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/misc/eeprom/at24.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 625b00166..9e9fe69b4 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -621,9 +621,10 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 
 	/* use dummy devices for multiple-address chips */
 	for (i = 1; i < num_addresses; i++) {
-		at24->client[i].client = i2c_new_dummy(client->adapter,
-						       client->addr + i);
-		if (!at24->client[i].client) {
+		at24->client[i].client = devm_i2c_new_dummy(&client->dev,
+							    client->adapter,
+							    client->addr + i);
+		if (IS_ERR(at24->client[i].client)) {
 			dev_err(&client->dev, "address 0x%02x unavailable\n",
 					client->addr + i);
 			err = -EADDRINUSE;
@@ -686,10 +687,6 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	return 0;
 
 err_clients:
-	for (i = 1; i < num_addresses; i++)
-		if (at24->client[i].client)
-			i2c_unregister_device(at24->client[i].client);
-
 	pm_runtime_disable(&client->dev);
 
 	return err;
@@ -698,15 +695,11 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 static int at24_remove(struct i2c_client *client)
 {
 	struct at24_data *at24;
-	int i;
 
 	at24 = i2c_get_clientdata(client);
 
 	nvmem_unregister(at24->nvmem);
 
-	for (i = 1; i < at24->num_addresses; i++)
-		i2c_unregister_device(at24->client[i].client);
-
 	pm_runtime_disable(&client->dev);
 	pm_runtime_set_suspended(&client->dev);
 
-- 
2.15.1

Re: [PATCH resubmit 1/2] i2c: core: add device-managed version of i2c_new_dummy

[Bartosz Golaszewski]

2017-12-05 20:44 GMT+01:00 Heiner Kallweit <hkallweit1@gmail.com>:
> 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@gmail.com>
> Reviewed-by: Peter Rosin <peda@axentia.se>
> ---
>  Documentation/driver-model/devres.txt |  3 +++
>  drivers/i2c/i2c-core-base.c           | 39 +++++++++++++++++++++++++++++++++++
>  include/linux/i2c.h                   |  3 +++
>  3 files changed, 45 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 bf52cca87..c1db67f9a 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -820,6 +820,45 @@ 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);
> +}
> +

Wolfram will have the last word here, but I would really prefer that
you wrap struct i2c_client in a separate devres (e.g. struct
i2c_dummy_devres) structure and avoid the cast. I find it a lot more
readable even if it only has a single member.

> +/**
> + * 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);
> +
> +       ret = i2c_new_dummy(adapter, address);
> +       if (!ret) {
> +               devres_free(dr);
> +               return ERR_PTR(-EBUSY);

This is misleading as EBUSY is not necessarily the error that cased
i2c_new_device() to fail. Return NULL here and document that users
need to use IS_ERR_OR_NULL() to check for errors.

> +       }
> +
> +       *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 a556db976..c27eac1e1 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -383,6 +383,9 @@ 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
>
>

Thanks,
Bartosz

Re: [PATCH resubmit 1/2] i2c: core: add device-managed version of i2c_new_dummy

[Heiner Kallweit]

Am 06.12.2017 um 11:36 schrieb Bartosz Golaszewski:
> 2017-12-05 20:44 GMT+01:00 Heiner Kallweit <hkallweit1@gmail.com>:
>> 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@gmail.com>
>> Reviewed-by: Peter Rosin <peda@axentia.se>
>> ---
>>  Documentation/driver-model/devres.txt |  3 +++
>>  drivers/i2c/i2c-core-base.c           | 39 +++++++++++++++++++++++++++++++++++
>>  include/linux/i2c.h                   |  3 +++
>>  3 files changed, 45 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 bf52cca87..c1db67f9a 100644
>> --- a/drivers/i2c/i2c-core-base.c
>> +++ b/drivers/i2c/i2c-core-base.c
>> @@ -820,6 +820,45 @@ 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);
>> +}
>> +
> 
> Wolfram will have the last word here, but I would really prefer that
> you wrap struct i2c_client in a separate devres (e.g. struct
> i2c_dummy_devres) structure and avoid the cast. I find it a lot more
> readable even if it only has a single member.
> 
This cast is a very common pattern in such release callbacks, see e.g.
devm_spi_unregister.

>> +/**
>> + * 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);
>> +
>> +       ret = i2c_new_dummy(adapter, address);
>> +       if (!ret) {
>> +               devres_free(dr);
>> +               return ERR_PTR(-EBUSY);
> 
> This is misleading as EBUSY is not necessarily the error that cased
> i2c_new_device() to fail. Return NULL here and document that users
> need to use IS_ERR_OR_NULL() to check for errors.
> 
Indeed returning a fixed error code -EBUSY may not be the best choice.
I have another alternative in mind:
i2c_new_device brings everything to return a detailed error code.
I think of splitting this function into a main function returning
a detailed error code and a compatibility wrapper which returns NULL
in error case, thus keeping the API stable.
I will submit a proposal.

>> +       }
>> +
>> +       *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 a556db976..c27eac1e1 100644
>> --- a/include/linux/i2c.h
>> +++ b/include/linux/i2c.h
>> @@ -383,6 +383,9 @@ 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
>>
>>
> 
> Thanks,
> Bartosz
>