linux-kernel - Re: [PATCH v3 1/2] ACPI: IPMI: Add helper to wait for when SMI is selected

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Message-ID: <CAAd53p4iLK1gJPgrpr5AuB2WEFYD263RW3VKC9FUp3TgZ54Kvw@mail.gmail.com>
Date: Fri, 5 Jan 2024 12:54:40 +0800
From: Kai-Heng Feng <kai.heng.feng@...onical.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: jdelvare@...e.com, linux@...ck-us.net, Len Brown <lenb@...nel.org>, 
	Robert Moore <robert.moore@...el.com>, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, acpica-devel@...ts.linux.dev
Subject: Re: [PATCH v3 1/2] ACPI: IPMI: Add helper to wait for when SMI is selected

On Fri, Jan 5, 2024 at 1:25 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> <kai.heng.feng@...onical.com> wrote:
> >
> > The function of acpi_power_meter module on Dell system requires IPMI
> > handler is installed and SMI is selected.
> >
> > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > are ready.
>
> The changelog is a bit terse.
>
> It could describe the problem at hand in more detail, for example.
>
> Also it wouldn't hurt to provide a Link: tag pointing to a place where
> some extra details could be found.

OK. Will add more info in next revision.

>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> > v3:
> >  - New patch.
> >
> >  drivers/acpi/acpi_ipmi.c | 17 ++++++++++++++++-
> >  include/acpi/acpi_bus.h  |  5 +++++
> >  2 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
> > index 0555f68c2dfd..54862cab7171 100644
> > --- a/drivers/acpi/acpi_ipmi.c
> > +++ b/drivers/acpi/acpi_ipmi.c
> > @@ -23,6 +23,8 @@ MODULE_LICENSE("GPL");
> >  #define IPMI_TIMEOUT                   (5000)
> >  #define ACPI_IPMI_MAX_MSG_LENGTH       64
> >
> > +static struct completion smi_selected;
> > +
> >  struct acpi_ipmi_device {
> >         /* the device list attached to driver_data.ipmi_devices */
> >         struct list_head head;
> > @@ -463,8 +465,10 @@ static void ipmi_register_bmc(int iface, struct device *dev)
> >                 if (temp->handle == handle)
> >                         goto err_lock;
> >         }
> > -       if (!driver_data.selected_smi)
> > +       if (!driver_data.selected_smi) {
> >                 driver_data.selected_smi = ipmi_device;
> > +               complete(&smi_selected);
>
> It looks like the new completion is at least related to driver_data,
> so should it be a member of the latter?

Sure thing.

>
> > +       }
> >         list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
> >         mutex_unlock(&driver_data.ipmi_lock);
> >
> > @@ -578,10 +582,21 @@ acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
> >         return status;
> >  }
> >
> > +int acpi_wait_for_acpi_ipmi(void)
> > +{
> > +       long ret;
> > +
> > +       ret = wait_for_completion_interruptible_timeout(&smi_selected, 2 * HZ);
>
> Why does it wait for 2 ticks and not 3 or 5?
>
> Also it would be nice to have a symbol defined for this timeout value.

Sure. Will add a define and comment.

>
> > +
> > +       return ret > 0 ? 0 : -ETIMEDOUT;
>
> if (ret <= 0)
>         return -ETIMEDOUT;
>
> return 0;
>
> pretty please.

OK.

>
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> > +
> >  static int __init acpi_ipmi_init(void)
> >  {
> >         int result;
> >         acpi_status status;
>
> Empty line here, please.

OK.

>
> > +       init_completion(&smi_selected);
>
> Does it really make sense to initialize it when ACPI is disabled?

OK, will move it further down.

Kai-Heng

>
> >
> >         if (acpi_disabled)
> >                 return 0;
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index 1216d72c650f..afa6e4d4bf46 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -821,11 +821,16 @@ static inline void acpi_put_acpi_dev(struct acpi_device *adev)
> >  {
> >         acpi_dev_put(adev);
> >  }
> > +
> > +int acpi_wait_for_acpi_ipmi(void);
> > +
> >  #else  /* CONFIG_ACPI */
> >
> >  static inline int register_acpi_bus_type(void *bus) { return 0; }
> >  static inline int unregister_acpi_bus_type(void *bus) { return 0; }
> >
> > +static inline int acpi_wait_for_acpi_ipmi(void) { return 0; }
> > +
> >  #endif                         /* CONFIG_ACPI */
> >
> >  #endif /*__ACPI_BUS_H__*/
> > --