Re: [PATCH 1/5] ACPI: battery: Do not unload battery hooks on single error

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Am 19.09.22 um 21:12 schrieb Armin Wolf:

Am 19.09.22 um 18:27 schrieb Rafael J. Wysocki:

On Mon, Sep 19, 2022 at 12:42 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi,

On 9/12/22 13:53, Armin Wolf wrote:
Currently, battery hooks are being unloaded if they return
an error when adding a single battery.
This however also causes the removal of successfully added
hooks if they return -ENODEV for a single unsupported
battery.

Do not unload battery hooks in such cases since the hook
handles any cleanup actions.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
Maybe instead of removing all error checking, allow -ENODEV
and behave as before when the error is not -ENODEV ?

Otherwise we should probably make the add / remove callbacks
void to indicate that any errors are ignored.

Rafael, do you have any opinion on this?
IMV this is not a completely safe change, because things may simply
not work in the cases in which an error is returned.

It would be somewhat better to use a special error code to indicate
"no support" (eg. -ENOTSUPP) and ignore that one only.

I would favor -ENODEV then, since it is already used by quiet a few drivers
to indicate a unsupported battery.

Armin Wolf

While checking all instances where the battery hook mechanism is currently used,
i found out that all but a single battery hook return -ENODEV for all errors they
encounter, the exception being the huawei-wmi driver.

I do not know the reason for this, but i fear unloading the extension on for
example -ENOTSUP will result in similar behavior by hooks wanting to avoid being
unloaded on harmless errors.

However, i agree that when ignoring all errors, battery extensions which provide
similar attributes may currently delete each others attributes.

Any idea on how to solve this?

Armin Wolf

---
  drivers/acpi/battery.c | 24 +++---------------------
  1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 306513fec1e1..e59c261c7c59 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -724,20 +724,10 @@ void battery_hook_register(struct acpi_battery_hook *hook)
        * its attributes.
        */
       list_for_each_entry(battery, &acpi_battery_list, list) {
-             if (hook->add_battery(battery->bat)) {
-                     /*
-                      * If a add-battery returns non-zero,
-                      * the registration of the extension has failed,
-                      * and we will not add it to the list of loaded
-                      * hooks.
-                      */
-                     pr_err("extension failed to load: %s", hook->name);
-                     __battery_hook_unregister(hook, 0);
-                     goto end;
-             }
+             hook->add_battery(battery->bat);
       }
       pr_info("new extension: %s\n", hook->name);
-end:
+
       mutex_unlock(&hook_mutex);
  }
  EXPORT_SYMBOL_GPL(battery_hook_register);
@@ -762,15 +752,7 @@ static void battery_hook_add_battery(struct acpi_battery *battery)
        * during the battery module initialization.
        */
       list_for_each_entry_safe(hook_node, tmp, &battery_hook_list, list) {
-             if (hook_node->add_battery(battery->bat)) {
-                     /*
-                      * The notification of the extensions has failed, to -                      * prevent further errors we will unload the extension.
-                      */
-                     pr_err("error in extension, unloading: %s",
-                                     hook_node->name);
-                     __battery_hook_unregister(hook_node, 0);
-             }
+             hook_node->add_battery(battery->bat);
       }
       mutex_unlock(&hook_mutex);
  }
--
2.30.2





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