acpi: indicate to platform when hot remove returns busy

In hotplug logic, it always indicates non-specific failure to platform through _OST when handing acpi hot-remove event failed. Then platform terminates the hot-remove process but it can not identify the reason.

Base on current hot-remove code, there have two situations that it returns busy:
- OSPM try to offline an individual device, but the device offline function returns busy.
- When the ejection event is applied to an "not offlined yet" container. OSPM send kobject change event to userspace and returns busy.

Both of them will returns -EBUSY to acpi device hotplug function then hotplug function indicates non-specific failure to platform just like any other error, e.g. -ENODEV or -EIO.

The benefit to platform for identifying the OS busy state is that platform can be applied different approach to handle the busy but not just terminate the hot-remove process by unknown reason. For example, platform can wait for a while then triggers hot-remove again.

This RFC patch adds one more parameter to the handler function of acpi generic hotplug event to give the function a chance to propose the return code of _OST. In this case, it sets ost return code to ACPI_OST_SC_DEVICE_BUSY when the acpi hot remove function returns -EBUSY.

v4:
Use switch-case statements to simplify code. (Andy Shevchenko, Rafael J. Wysocki)

v3:
Removed redundant 'else' in acpi_ost_status_code(). (Andy Shevchenko)

v2:
Do not overwrite ost code in acpi_generic_hotplug_event(). Move the "error code to ost code" logic to a help function. (Andy Shevchenko)

Cc "Rafael J. Wysocki" <[email protected]>

Cc Len Brown <[email protected]>

Cc Andy Shevchenko <[email protected]>

Cc Michal Hocko <[email protected]>

Signed-off-by "Lee, Chun-Yi" <[email protected]>

---
 drivers/acpi/scan.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

drivers/acpi/scan.c +13 -6

index d531629..ce88175 100644
@@ -404,10 +404,6 @@ void acpi_device_hotplug(struct acpi_device *adev, u32 src)
                error = dock_notify(adev, src);
        } else if (adev->flags.hotplug_notify) {
                error = acpi_generic_hotplug_event(adev, src);
-               if (error == -EPERM) {
-                       ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
-                       goto err_out;
-               }
        } else {
                int (*notify)(struct acpi_device *, u32);
 

@@ -423,8 +419,20 @@ void acpi_device_hotplug(struct acpi_device *adev, u32 src)
                else
                        goto out;
        }
-       if (!error)
+       switch (error) {
+       case 0:
                ost_code = ACPI_OST_SC_SUCCESS;
+               break;
+       case -EPERM:
+               ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
+               break;
+       case -EBUSY:
+               ost_code = ACPI_OST_SC_DEVICE_BUSY;
+               break;
+       default:
+               ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
+               break;
+       }
 
  err_out:
        acpi_evaluate_ost(adev->handle, src, ost_code, NULL);
--

2.10.2