Re: [PATCH v2] extcon: fix extcon_get_extcon_dev() error handling

Heikki Krogerus
2021-11-23T15:20:08Z

On Tue, Nov 23, 2021 at 11:43:06AM +0300, 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>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.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");

--
heikki