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

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

[Kai-Heng Feng]

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.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
+	}
 	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);
+
+	return ret > 0 ? 0 : -ETIMEDOUT;
+}
+EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
+
 static int __init acpi_ipmi_init(void)
 {
 	int result;
 	acpi_status status;
+	init_completion(&smi_selected);
 
 	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__*/
-- 
2.34.1

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

[Rafael J. Wysocki]

On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
<kai.heng.feng@canonical.com> wrote:
>
> The function of acpi_power_meter module on Dell system requires IPMI
> handler is installed and SMI is selected.

Does the firmware use _DEP to let the OS know about this dependency?

> So add a helper to let acpi_power_meter know when IPMI handler and SMI
> are ready.
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
> +       }
>         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);
> +
> +       return ret > 0 ? 0 : -ETIMEDOUT;

What will happen if the IPMI driver is unloaded after this has returned 0?

> +}
> +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> +
>  static int __init acpi_ipmi_init(void)
>  {
>         int result;
>         acpi_status status;
> +       init_completion(&smi_selected);
>
>         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__*/
> --

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

[Corey Minyard]

On Thu, Jan 04, 2024 at 02:34:52PM +0100, Rafael J. Wysocki wrote:
> On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> <kai.heng.feng@canonical.com> wrote:
> >
> > The function of acpi_power_meter module on Dell system requires IPMI
> > handler is installed and SMI is selected.
> 
> Does the firmware use _DEP to let the OS know about this dependency?
> 
> > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > are ready.
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
> > +       }
> >         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);
> > +
> > +       return ret > 0 ? 0 : -ETIMEDOUT;
> 
> What will happen if the IPMI driver is unloaded after this has returned 0?

The IPMI driver can't be unloaded if it has a user.

I've been following this, but I know little about ACPI.  Beyond this
solution, the only other solution I could come up with was to start the
IPMI driver earlier.  But then you are in a chicken-and-egg situation
(https://dictionary.cambridge.org/dictionary/english/chicken-and-egg-situation).
Which was the reason for the SPMI table, but that's really kind of
useless for this, even if the SPMI table existed.

-corey

> 
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> > +
> >  static int __init acpi_ipmi_init(void)
> >  {
> >         int result;
> >         acpi_status status;
> > +       init_completion(&smi_selected);
> >
> >         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__*/
> > --
> 

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

[Rafael J. Wysocki]

On Thu, Jan 4, 2024 at 4:42 PM Corey Minyard <minyard@acm.org> wrote:
>
> On Thu, Jan 04, 2024 at 02:34:52PM +0100, Rafael J. Wysocki wrote:
> > On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> > <kai.heng.feng@canonical.com> wrote:
> > >
> > > The function of acpi_power_meter module on Dell system requires IPMI
> > > handler is installed and SMI is selected.
> >
> > Does the firmware use _DEP to let the OS know about this dependency?
> >
> > > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > > are ready.
> > >
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
> > > +       }
> > >         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);
> > > +
> > > +       return ret > 0 ? 0 : -ETIMEDOUT;
> >
> > What will happen if the IPMI driver is unloaded after this has returned 0?
>
> The IPMI driver can't be unloaded if it has a user.

Because of the use of the exported symbol, right?

> I've been following this, but I know little about ACPI.  Beyond this
> solution, the only other solution I could come up with was to start the
> IPMI driver earlier.  But then you are in a chicken-and-egg situation
> (https://dictionary.cambridge.org/dictionary/english/chicken-and-egg-situation).
> Which was the reason for the SPMI table, but that's really kind of
> useless for this, even if the SPMI table existed.

Fine.

Let me reply to the patch with some more comments then.

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

[Rafael J. Wysocki]

On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
<kai.heng.feng@canonical.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.

> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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?

> +       }
>         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.

> +
> +       return ret > 0 ? 0 : -ETIMEDOUT;

if (ret <= 0)
        return -ETIMEDOUT;

return 0;

pretty please.

> +}
> +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> +
>  static int __init acpi_ipmi_init(void)
>  {
>         int result;
>         acpi_status status;

Empty line here, please.

> +       init_completion(&smi_selected);

Does it really make sense to initialize it when ACPI is disabled?

>
>         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__*/
> --

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

[Corey Minyard]

On Thu, Jan 04, 2024 at 06:11:29PM +0100, Rafael J. Wysocki wrote:
> On Thu, Jan 4, 2024 at 4:42 PM Corey Minyard <minyard@acm.org> wrote:
> >
> > On Thu, Jan 04, 2024 at 02:34:52PM +0100, Rafael J. Wysocki wrote:
> > > On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> > > <kai.heng.feng@canonical.com> wrote:
> > > >
> > > > The function of acpi_power_meter module on Dell system requires IPMI
> > > > handler is installed and SMI is selected.
> > >
> > > Does the firmware use _DEP to let the OS know about this dependency?
> > >
> > > > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > > > are ready.
> > > >
> > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
> > > > +       }
> > > >         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);
> > > > +
> > > > +       return ret > 0 ? 0 : -ETIMEDOUT;
> > >
> > > What will happen if the IPMI driver is unloaded after this has returned 0?
> >
> > The IPMI driver can't be unloaded if it has a user.
> 
> Because of the use of the exported symbol, right?

I wasn't thinking that, but yes, that would do it.  It also keep track
of users and doesn't allow the driver to be unloaded if anything has
registered as a user, either.

-corey

> 
> > I've been following this, but I know little about ACPI.  Beyond this
> > solution, the only other solution I could come up with was to start the
> > IPMI driver earlier.  But then you are in a chicken-and-egg situation
> > (https://dictionary.cambridge.org/dictionary/english/chicken-and-egg-situation).
> > Which was the reason for the SPMI table, but that's really kind of
> > useless for this, even if the SPMI table existed.
> 
> Fine.
> 
> Let me reply to the patch with some more comments then.

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

[Kai-Heng Feng]

On Thu, Jan 4, 2024 at 9:35 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> <kai.heng.feng@canonical.com> wrote:
> >
> > The function of acpi_power_meter module on Dell system requires IPMI
> > handler is installed and SMI is selected.
>
> Does the firmware use _DEP to let the OS know about this dependency?

No. _DEP is missing.

Kai-Heng

>
> > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > are ready.
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.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);
> > +       }
> >         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);
> > +
> > +       return ret > 0 ? 0 : -ETIMEDOUT;
>
> What will happen if the IPMI driver is unloaded after this has returned 0?
>
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> > +
> >  static int __init acpi_ipmi_init(void)
> >  {
> >         int result;
> >         acpi_status status;
> > +       init_completion(&smi_selected);
> >
> >         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__*/
> > --

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

[Kai-Heng Feng]

On Fri, Jan 5, 2024 at 1:25 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> <kai.heng.feng@canonical.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@canonical.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__*/
> > --