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    SubjectRe: [PATCH v2] extcon: fix extcon_get_extcon_dev() error handling
    Date
    Hi Dan,

    First of all, sorry for late reply.

    There is one issue. About this issue, I already discussed on patch[1]
    [1] https://lore.kernel.org/lkml/5BEB63C3.1020504@samsung.com/

    extcon_get_extcon_dev() is used for anywhere except for probe step.
    But EPROBE_DEFER is only used on probe step.

    So that it is not clear to return EPROBE_DEFER from extcon_get_extcon_dev()
    because extcon_get_extcon_dev() never know either call it on probe function
    or not.


    On 11/23/21 5:43 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
    >
    > If we apply this patch, it might be a good idea to send it to -stable
    > so that backported code that relies on handling error pointers does
    > not break silently.
    >
    > drivers/extcon/extcon-axp288.c | 4 ++--
    > drivers/extcon/extcon.c | 2 +-
    > 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 ++--
    > include/linux/extcon.h | 2 +-
    > 9 files changed, 27 insertions(+), 32 deletions(-)
    >
    > diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
    > index e7a9561a826d..a35e99928807 100644
    > --- a/drivers/extcon/extcon.c
    > +++ b/drivers/extcon/extcon.c
    > @@ -876,7 +876,7 @@ 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

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