[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@xxxxxxxxxxxxx>
---
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