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

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

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");
>>
> 
> 
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics