i2c: core: add device-managed version of i2c_new_dummy

Message ID de2f844a-9d41-fa0e-cd55-fc7d2cea24d5@gmail.com
State Superseded
Delegated to: Bartosz Golaszewski
Headers show

Commit Message

Heiner Kallweit Aug. 21, 2017, 6:24 p.m.
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.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/i2c/i2c-core-base.c | 29 +++++++++++++++++++++++++++++
 include/linux/i2c.h         |  3 +++
 2 files changed, 32 insertions(+)

Comments

Peter Rosin Aug. 21, 2017, 6:42 p.m. | #1
Hi!

On 2017-08-21 20:24, Heiner Kallweit wrote:
> 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.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/i2c/i2c-core-base.c | 29 +++++++++++++++++++++++++++++
>  include/linux/i2c.h         |  3 +++
>  2 files changed, 32 insertions(+)

You need to update Documentation/driver-model/devres.txt

> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 12822a4b..7eb48328 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -868,6 +868,35 @@ 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);
> +}
> +
> +/* managed version of i2c_new_dummy */

A kernel-doc comment is preferred for public functions. Especially new
functions...

> +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 NULL;

Would it not be splendid if you returned an error pointer
instead, preferably you should also change the i2c_new_dummy
interface (don't forget to update callers) to return such a
thing instead of NULL on error so that -EBUSY etc is
propagated? But there are a few dozen callers, I don't know
if it's worth it at this point?

Anyway, if we do it right for the managed function from the
start, that count of i2c_new_dummy callers might get more
manageable in the future?

Cheers,
peda

> +
> +	ret = i2c_new_dummy(adapter, address);
> +	if (!ret) {
> +		devres_free(dr);
> +		return NULL;
> +	}
> +
> +	*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 d501d395..d0c091e6 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -381,6 +381,9 @@ 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,
>
Heiner Kallweit Aug. 21, 2017, 7:56 p.m. | #2
Am 21.08.2017 um 20:42 schrieb Peter Rosin:
> Hi!
> 
> On 2017-08-21 20:24, Heiner Kallweit wrote:
>> 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.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>> ---
>>  drivers/i2c/i2c-core-base.c | 29 +++++++++++++++++++++++++++++
>>  include/linux/i2c.h         |  3 +++
>>  2 files changed, 32 insertions(+)
> 
> You need to update Documentation/driver-model/devres.txt
> 
Right, thanks for the hint.

>> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
>> index 12822a4b..7eb48328 100644
>> --- a/drivers/i2c/i2c-core-base.c
>> +++ b/drivers/i2c/i2c-core-base.c
>> @@ -868,6 +868,35 @@ 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);
>> +}
>> +
>> +/* managed version of i2c_new_dummy */
> 
> A kernel-doc comment is preferred for public functions. Especially new
> functions...
> 
OK

>> +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 NULL;
> 
> Would it not be splendid if you returned an error pointer
> instead, preferably you should also change the i2c_new_dummy
> interface (don't forget to update callers) to return such a
> thing instead of NULL on error so that -EBUSY etc is
> propagated? But there are a few dozen callers, I don't know
> if it's worth it at this point?
> 
i2c_new_dummy does little more than calling i2c_new_device
which returns NULL in case of an error. So we would have to
change i2c_new_device too. This may be a little too ambitious.

When talking about changing the interface:
devm_i2c_new_dummy usually will be called with parameters

dev = &client->dev and
adapter = client->adapter

So we could change and simplify it to
struct i2c_client *devm_i2c_new_dummy(struct i2c_client *client, u16 address)

However maintainers usually insist on first parameter of a devm_
function has to be a struct device *, although there are existing
devm_ functions like devm_regmap_init_i2c not following this rule.

I'd appreciate feedback whether it would be acceptable in our case.

> Anyway, if we do it right for the managed function from the
> start, that count of i2c_new_dummy callers might get more
> manageable in the future?
> 
> Cheers,
> peda
> 
>> +
>> +	ret = i2c_new_dummy(adapter, address);
>> +	if (!ret) {
>> +		devres_free(dr);
>> +		return NULL;
>> +	}
>> +
>> +	*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 d501d395..d0c091e6 100644
>> --- a/include/linux/i2c.h
>> +++ b/include/linux/i2c.h
>> @@ -381,6 +381,9 @@ 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,
>>
> 
>
Peter Rosin Aug. 21, 2017, 9:28 p.m. | #3
On 2017-08-21 21:56, Heiner Kallweit wrote:
> Am 21.08.2017 um 20:42 schrieb Peter Rosin:
>> Hi!
>>
>> On 2017-08-21 20:24, Heiner Kallweit wrote:
>>> 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.
>>>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>> ---
>>>  drivers/i2c/i2c-core-base.c | 29 +++++++++++++++++++++++++++++
>>>  include/linux/i2c.h         |  3 +++
>>>  2 files changed, 32 insertions(+)
>>
>> You need to update Documentation/driver-model/devres.txt
>>
> Right, thanks for the hint.
> 
>>> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
>>> index 12822a4b..7eb48328 100644
>>> --- a/drivers/i2c/i2c-core-base.c
>>> +++ b/drivers/i2c/i2c-core-base.c
>>> @@ -868,6 +868,35 @@ 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);
>>> +}
>>> +
>>> +/* managed version of i2c_new_dummy */
>>
>> A kernel-doc comment is preferred for public functions. Especially new
>> functions...
>>
> OK
> 
>>> +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 NULL;
>>
>> Would it not be splendid if you returned an error pointer
>> instead, preferably you should also change the i2c_new_dummy
>> interface (don't forget to update callers) to return such a
>> thing instead of NULL on error so that -EBUSY etc is
>> propagated? But there are a few dozen callers, I don't know
>> if it's worth it at this point?
>>
> i2c_new_dummy does little more than calling i2c_new_device
> which returns NULL in case of an error. So we would have to
> change i2c_new_device too. This may be a little too ambitious.

Yes and no.

Yes, it is ambitious, but the right thing to do in the end. And
it is mechanical, so it is not really hard. But I already said that
it might not be worth it at this point...

No, we do not have to follow the return value convention from
i2c_new_dummy in devm_i2c_new_dummy. What I meant below was that
for the time being devm_i2c_new_dummy can return ERR_PTR(-Ewhatever)
when i2c_new_dummy returns NULL. Then, when most/all i2c_new_dummy
users have been converted over to devm_i2c_new_dummy (which might
take a while) it will be less daunting to convert i2c_new_dummy to
not return a plain old boring NULL on failure. And then it will be
really easy to change devm_i2c_new_dummy to propagate that value w/o
causing massive churn in all callers at once.

> When talking about changing the interface:
> devm_i2c_new_dummy usually will be called with parameters
> 
> dev = &client->dev and
> adapter = client->adapter
> 
> So we could change and simplify it to
> struct i2c_client *devm_i2c_new_dummy(struct i2c_client *client, u16 address)
> 
> However maintainers usually insist on first parameter of a devm_
> function has to be a struct device *, although there are existing
> devm_ functions like devm_regmap_init_i2c not following this rule.
> 
> I'd appreciate feedback whether it would be acceptable in our case.

It would probably be good to target that question with an audience
a bit wider than the i2c list. Not sure where exactly it fits best
though?

Cheers,
peda

>> Anyway, if we do it right for the managed function from the
>> start, that count of i2c_new_dummy callers might get more
>> manageable in the future?
>>
>> Cheers,
>> peda
>>
>>> +
>>> +	ret = i2c_new_dummy(adapter, address);
>>> +	if (!ret) {
>>> +		devres_free(dr);
>>> +		return NULL;
>>> +	}
>>> +
>>> +	*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 d501d395..d0c091e6 100644
>>> --- a/include/linux/i2c.h
>>> +++ b/include/linux/i2c.h
>>> @@ -381,6 +381,9 @@ 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,
>>>
>>
>>
>
Heiner Kallweit Aug. 22, 2017, 5:39 a.m. | #4
Am 21.08.2017 um 23:28 schrieb Peter Rosin:
> On 2017-08-21 21:56, Heiner Kallweit wrote:
>> Am 21.08.2017 um 20:42 schrieb Peter Rosin:
>>> Hi!
>>>
>>> On 2017-08-21 20:24, Heiner Kallweit wrote:
>>>> 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.
>>>>
>>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>>> ---
>>>>  drivers/i2c/i2c-core-base.c | 29 +++++++++++++++++++++++++++++
>>>>  include/linux/i2c.h         |  3 +++
>>>>  2 files changed, 32 insertions(+)
>>>
>>> You need to update Documentation/driver-model/devres.txt
>>>
>> Right, thanks for the hint.
>>
>>>> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
>>>> index 12822a4b..7eb48328 100644
>>>> --- a/drivers/i2c/i2c-core-base.c
>>>> +++ b/drivers/i2c/i2c-core-base.c
>>>> @@ -868,6 +868,35 @@ 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);
>>>> +}
>>>> +
>>>> +/* managed version of i2c_new_dummy */
>>>
>>> A kernel-doc comment is preferred for public functions. Especially new
>>> functions...
>>>
>> OK
>>
>>>> +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 NULL;
>>>
>>> Would it not be splendid if you returned an error pointer
>>> instead, preferably you should also change the i2c_new_dummy
>>> interface (don't forget to update callers) to return such a
>>> thing instead of NULL on error so that -EBUSY etc is
>>> propagated? But there are a few dozen callers, I don't know
>>> if it's worth it at this point?
>>>
>> i2c_new_dummy does little more than calling i2c_new_device
>> which returns NULL in case of an error. So we would have to
>> change i2c_new_device too. This may be a little too ambitious.
> 
> Yes and no.
> 
> Yes, it is ambitious, but the right thing to do in the end. And
> it is mechanical, so it is not really hard. But I already said that
> it might not be worth it at this point...
> 
> No, we do not have to follow the return value convention from
> i2c_new_dummy in devm_i2c_new_dummy. What I meant below was that
> for the time being devm_i2c_new_dummy can return ERR_PTR(-Ewhatever)
> when i2c_new_dummy returns NULL. Then, when most/all i2c_new_dummy
> users have been converted over to devm_i2c_new_dummy (which might
> take a while) it will be less daunting to convert i2c_new_dummy to
> not return a plain old boring NULL on failure. And then it will be
> really easy to change devm_i2c_new_dummy to propagate that value w/o
> causing massive churn in all callers at once.
> 
I see, yes this would make sense IMHO.

>> When talking about changing the interface:
>> devm_i2c_new_dummy usually will be called with parameters
>>
>> dev = &client->dev and
>> adapter = client->adapter
>>
>> So we could change and simplify it to
>> struct i2c_client *devm_i2c_new_dummy(struct i2c_client *client, u16 address)
>>
>> However maintainers usually insist on first parameter of a devm_
>> function has to be a struct device *, although there are existing
>> devm_ functions like devm_regmap_init_i2c not following this rule.
>>
>> I'd appreciate feedback whether it would be acceptable in our case.
> 
> It would probably be good to target that question with an audience
> a bit wider than the i2c list. Not sure where exactly it fits best
> though?
> 
I think for now I will skip this as there are few users of
i2c_new_dummy using it with the i2c client being provided by a
parent device. Example: drivers/rtc/rtc-s5m.c

Rgds, Heiner

> Cheers,
> peda
> 
>>> Anyway, if we do it right for the managed function from the
>>> start, that count of i2c_new_dummy callers might get more
>>> manageable in the future?
>>>
>>> Cheers,
>>> peda
>>>
>>>> +
>>>> +	ret = i2c_new_dummy(adapter, address);
>>>> +	if (!ret) {
>>>> +		devres_free(dr);
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>> +	*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 d501d395..d0c091e6 100644
>>>> --- a/include/linux/i2c.h
>>>> +++ b/include/linux/i2c.h
>>>> @@ -381,6 +381,9 @@ 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,
>>>>
>>>
>>>
>>
> 
>

Patch

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 12822a4b..7eb48328 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -868,6 +868,35 @@  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);
+}
+
+/* managed version of i2c_new_dummy */
+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 NULL;
+
+	ret = i2c_new_dummy(adapter, address);
+	if (!ret) {
+		devres_free(dr);
+		return NULL;
+	}
+
+	*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 d501d395..d0c091e6 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -381,6 +381,9 @@  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,