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

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Message-ID: <CAJZ5v0jWVMMTjc+KtBRS86f8kYpbPcDCH9JV2ZgeN4f-MSO8rQ@mail.gmail.com>
Date:   Mon, 19 Sep 2022 18:27:24 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Armin Wolf <W_Armin@....de>, Mark Gross <markgross@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Henrique de Moraes Holschuh <hmh@....eng.br>,
        Matan Ziv-Av <matan@...alib.org>,
        Corentin Chary <corentin.chary@...il.com>,
        Jeremy Soller <jeremy@...tem76.com>, productdev@...tem76.com,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] ACPI: battery: Do not unload battery hooks on single error

On Mon, Sep 19, 2022 at 12:42 PM Hans de Goede <hdegoede@...hat.com> 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@....de>
>
> 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.

> > ---
> >  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
> >
>