Re: [PATCH v3] extcon: fix extcon_get_extcon_dev() error handling

[Chanwoo Choi <cw00.choi@samsung.com>]

Dear all,

Applied it. Thanks.

Best Regards,
Chanwoo Choi


On 2/3/22 2:24 PM, Chanwoo Choi wrote:
> Hi Felipe,
> 
> Gently Ping.
> 
> Best Regards,
> Chanwoo Choi
> 
> On 12/20/21 10:20 AM, Chanwoo Choi wrote:
>> Hi Sebastian and Felipe,
>>
>> If Sebastian and Felipe don't have any additional opinion,
>> could you please reply the review for this patch?
>>
>> And if Sebastian and Felipe agree, I'll merge it to extcon tree.
>>
>>
>> Best Regards,
>> Chanwoo Choi
>>
>>
>> On 12/17/21 3:28 PM, Dan Carpenter wrote:
>>> The extcon_get_extcon_dev() function returns error pointers on error,
>>> NULL when it's a -EPROBE_DEFER defer situation, and ERR_PTR(-ENODEV)
>>> when the CONFIG_EXTCON option is disabled.  This is very complicated for
>>> the callers to handle and a number of them had bugs that would lead to
>>> an Oops.
>>>
>>> In real life, there are two things which prevented crashes.  First,
>>> error pointers would only be returned if there was bug in the caller
>>> where they passed a NULL "extcon_name" and none of them do that.
>>> Second, only two out of the eight drivers will build when CONFIG_EXTCON
>>> is disabled.
>>>
>>> The normal way to write this would be to return -EPROBE_DEFER directly
>>> when appropriate and return NULL when CONFIG_EXTCON is disabled.  Then
>>> the error handling is simple and just looks like:
>>>
>>> 	dev->edev = extcon_get_extcon_dev(acpi_dev_name(adev));
>>> 	if (IS_ERR(dev->edev))
>>> 		return PTR_ERR(dev->edev);
>>>
>>> For the two drivers which can build with CONFIG_EXTCON disabled, then
>>> extcon_get_extcon_dev() will now return NULL which is not treated as an
>>> error and the probe will continue successfully.  Those two drivers are
>>> "typec_fusb302" and "max8997-battery".  In the original code, the
>>> typec_fusb302 driver had an 800ms hang in tcpm_get_current_limit() but
>>> now that function is a no-op.  For the max8997-battery driver everything
>>> should continue working as is.
>>>
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>> ---
>>> v2: return NULL when CONFIG_EXTCON is disabled
>>> v3: Add a note to extcon_get_extcon_dev() to say that it may only be
>>>     called from probe().
>>>
>>>  drivers/extcon/extcon.c                |  4 +++-
>>>  include/linux/extcon.h                 |  2 +-
>>>  drivers/extcon/extcon-axp288.c         |  4 ++--
>>>  drivers/power/supply/axp288_charger.c  | 17 ++++++++++-------
>>>  drivers/power/supply/charger-manager.c |  7 ++-----
>>>  drivers/power/supply/max8997_charger.c | 10 +++++-----
>>>  drivers/usb/dwc3/drd.c                 |  9 ++-------
>>>  drivers/usb/phy/phy-omap-otg.c         |  4 ++--
>>>  drivers/usb/typec/tcpm/fusb302.c       |  4 ++--
>>>  9 files changed, 29 insertions(+), 32 deletions(-)
>>>
>>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
>>> index e7a9561a826d..9eb92997f3ae 100644
>>> --- a/drivers/extcon/extcon.c
>>> +++ b/drivers/extcon/extcon.c
>>> @@ -863,6 +863,8 @@ EXPORT_SYMBOL_GPL(extcon_set_property_capability);
>>>   * @extcon_name:	the extcon name provided with extcon_dev_register()
>>>   *
>>>   * Return the pointer of extcon device if success or ERR_PTR(err) if fail.
>>> + * NOTE: This function returns -EPROBE_DEFER so it may only be called from
>>> + * probe() functions.
>>>   */
>>>  struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
>>>  {
>>> @@ -876,7 +878,7 @@ struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
>>>  		if (!strcmp(sd->name, extcon_name))
>>>  			goto out;
>>>  	}
>>> -	sd = NULL;
>>> +	sd = ERR_PTR(-EPROBE_DEFER);
>>>  out:
>>>  	mutex_unlock(&extcon_dev_list_lock);
>>>  	return sd;
>>> diff --git a/include/linux/extcon.h b/include/linux/extcon.h
>>> index 0c19010da77f..685401d94d39 100644
>>> --- a/include/linux/extcon.h
>>> +++ b/include/linux/extcon.h
>>> @@ -296,7 +296,7 @@ static inline void devm_extcon_unregister_notifier_all(struct device *dev,
>>>  
>>>  static inline struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
>>>  {
>>> -	return ERR_PTR(-ENODEV);
>>> +	return NULL;
>>>  }
>>>  
>>>  static inline struct extcon_dev *extcon_find_edev_by_node(struct device_node *node)
>>> diff --git a/drivers/extcon/extcon-axp288.c b/drivers/extcon/extcon-axp288.c
>>> index 7c6d5857ff25..180be768c215 100644
>>> --- a/drivers/extcon/extcon-axp288.c
>>> +++ b/drivers/extcon/extcon-axp288.c
>>> @@ -394,8 +394,8 @@ static int axp288_extcon_probe(struct platform_device *pdev)
>>>  		if (adev) {
>>>  			info->id_extcon = extcon_get_extcon_dev(acpi_dev_name(adev));
>>>  			put_device(&adev->dev);
>>> -			if (!info->id_extcon)
>>> -				return -EPROBE_DEFER;
>>> +			if (IS_ERR(info->id_extcon))
>>> +				return PTR_ERR(info->id_extcon);
>>>  
>>>  			dev_info(dev, "controlling USB role\n");
>>>  		} else {
>>> diff --git a/drivers/power/supply/axp288_charger.c b/drivers/power/supply/axp288_charger.c
>>> index ec41f6cd3f93..4acfeb52a44e 100644
>>> --- a/drivers/power/supply/axp288_charger.c
>>> +++ b/drivers/power/supply/axp288_charger.c
>>> @@ -848,17 +848,20 @@ static int axp288_charger_probe(struct platform_device *pdev)
>>>  	info->regmap_irqc = axp20x->regmap_irqc;
>>>  
>>>  	info->cable.edev = extcon_get_extcon_dev(AXP288_EXTCON_DEV_NAME);
>>> -	if (info->cable.edev == NULL) {
>>> -		dev_dbg(dev, "%s is not ready, probe deferred\n",
>>> -			AXP288_EXTCON_DEV_NAME);
>>> -		return -EPROBE_DEFER;
>>> +	if (IS_ERR(info->cable.edev)) {
>>> +		dev_err_probe(dev, PTR_ERR(info->cable.edev),
>>> +			      "extcon_get_extcon_dev(%s) failed\n",
>>> +			      AXP288_EXTCON_DEV_NAME);
>>> +		return PTR_ERR(info->cable.edev);
>>>  	}
>>>  
>>>  	if (acpi_dev_present(USB_HOST_EXTCON_HID, NULL, -1)) {
>>>  		info->otg.cable = extcon_get_extcon_dev(USB_HOST_EXTCON_NAME);
>>> -		if (info->otg.cable == NULL) {
>>> -			dev_dbg(dev, "EXTCON_USB_HOST is not ready, probe deferred\n");
>>> -			return -EPROBE_DEFER;
>>> +		if (IS_ERR(info->otg.cable)) {
>>> +			dev_err_probe(dev, PTR_ERR(info->otg.cable),
>>> +				      "extcon_get_extcon_dev(%s) failed\n",
>>> +				      USB_HOST_EXTCON_NAME);
>>> +			return PTR_ERR(info->otg.cable);
>>>  		}
>>>  		dev_info(dev, "Using " USB_HOST_EXTCON_HID " extcon for usb-id\n");
>>>  	}
>>> diff --git a/drivers/power/supply/charger-manager.c b/drivers/power/supply/charger-manager.c
>>> index d67edb760c94..92db79400a6a 100644
>>> --- a/drivers/power/supply/charger-manager.c
>>> +++ b/drivers/power/supply/charger-manager.c
>>> @@ -985,13 +985,10 @@ static int charger_extcon_init(struct charger_manager *cm,
>>>  	cable->nb.notifier_call = charger_extcon_notifier;
>>>  
>>>  	cable->extcon_dev = extcon_get_extcon_dev(cable->extcon_name);
>>> -	if (IS_ERR_OR_NULL(cable->extcon_dev)) {
>>> +	if (IS_ERR(cable->extcon_dev)) {
>>>  		pr_err("Cannot find extcon_dev for %s (cable: %s)\n",
>>>  			cable->extcon_name, cable->name);
>>> -		if (cable->extcon_dev == NULL)
>>> -			return -EPROBE_DEFER;
>>> -		else
>>> -			return PTR_ERR(cable->extcon_dev);
>>> +		return PTR_ERR(cable->extcon_dev);
>>>  	}
>>>  
>>>  	for (i = 0; i < ARRAY_SIZE(extcon_mapping); i++) {
>>> diff --git a/drivers/power/supply/max8997_charger.c b/drivers/power/supply/max8997_charger.c
>>> index 25207fe2aa68..634658adf313 100644
>>> --- a/drivers/power/supply/max8997_charger.c
>>> +++ b/drivers/power/supply/max8997_charger.c
>>> @@ -248,13 +248,13 @@ static int max8997_battery_probe(struct platform_device *pdev)
>>>  		dev_info(&pdev->dev, "couldn't get charger regulator\n");
>>>  	}
>>>  	charger->edev = extcon_get_extcon_dev("max8997-muic");
>>> -	if (IS_ERR_OR_NULL(charger->edev)) {
>>> -		if (!charger->edev)
>>> -			return -EPROBE_DEFER;
>>> -		dev_info(charger->dev, "couldn't get extcon device\n");
>>> +	if (IS_ERR(charger->edev)) {
>>> +		dev_err_probe(charger->dev, PTR_ERR(charger->edev),
>>> +			      "couldn't get extcon device: max8997-muic\n");
>>> +		return PTR_ERR(charger->edev);
>>>  	}
>>>  
>>> -	if (!IS_ERR(charger->reg) && !IS_ERR_OR_NULL(charger->edev)) {
>>> +	if (!IS_ERR(charger->reg)) {
>>>  		INIT_WORK(&charger->extcon_work, max8997_battery_extcon_evt_worker);
>>>  		ret = devm_add_action(&pdev->dev, max8997_battery_extcon_evt_stop_work, charger);
>>>  		if (ret) {
>>> diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
>>> index d7f76835137f..a490f79131c1 100644
>>> --- a/drivers/usb/dwc3/drd.c
>>> +++ b/drivers/usb/dwc3/drd.c
>>> @@ -454,13 +454,8 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
>>>  	 * This device property is for kernel internal use only and
>>>  	 * is expected to be set by the glue code.
>>>  	 */
>>> -	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
>>> -		edev = extcon_get_extcon_dev(name);
>>> -		if (!edev)
>>> -			return ERR_PTR(-EPROBE_DEFER);
>>> -
>>> -		return edev;
>>> -	}
>>> +	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0)
>>> +		return extcon_get_extcon_dev(name);
>>>  
>>>  	/*
>>>  	 * Try to get an extcon device from the USB PHY controller's "port"
>>> diff --git a/drivers/usb/phy/phy-omap-otg.c b/drivers/usb/phy/phy-omap-otg.c
>>> index ee0863c6553e..6e6ef8c0bc7e 100644
>>> --- a/drivers/usb/phy/phy-omap-otg.c
>>> +++ b/drivers/usb/phy/phy-omap-otg.c
>>> @@ -95,8 +95,8 @@ static int omap_otg_probe(struct platform_device *pdev)
>>>  		return -ENODEV;
>>>  
>>>  	extcon = extcon_get_extcon_dev(config->extcon);
>>> -	if (!extcon)
>>> -		return -EPROBE_DEFER;
>>> +	if (IS_ERR(extcon))
>>> +		return PTR_ERR(extcon);
>>>  
>>>  	otg_dev = devm_kzalloc(&pdev->dev, sizeof(*otg_dev), GFP_KERNEL);
>>>  	if (!otg_dev)
>>> diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
>>> index 72f9001b0792..96c55eaf3f80 100644
>>> --- a/drivers/usb/typec/tcpm/fusb302.c
>>> +++ b/drivers/usb/typec/tcpm/fusb302.c
>>> @@ -1708,8 +1708,8 @@ static int fusb302_probe(struct i2c_client *client,
>>>  	 */
>>>  	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
>>>  		chip->extcon = extcon_get_extcon_dev(name);
>>> -		if (!chip->extcon)
>>> -			return -EPROBE_DEFER;
>>> +		if (IS_ERR(chip->extcon))
>>> +			return PTR_ERR(chip->extcon);
>>>  	}
>>>  
>>>  	chip->vbus = devm_regulator_get(chip->dev, "vbus");
>>>
>>
>>
>>
>>
> 
>