ACPI: handle re-enumeration, when acpi_devices might already exist

acpi_bus_scan() traverses the namespace to enumerate devices and uses
acpi_add_single_object() to create acpi_devices.  When the platform
notifies us of a hot-plug event, we need to traverse part of the namespace
again to figure out what appeared or disappeared.  (We don't yet call
acpi_bus_scan() during hot-plug, but I plan to do that in the future.)

This patch makes acpi_add_single_object() notice when we already have
an acpi_device, so we don't need to make a new one.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 954bd01f295a..2c4cac576a7e 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1400,10 +1400,10 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl,
                                       void *context, void **return_value)
 {
         struct acpi_bus_ops *ops = context;
-        struct acpi_device *device = NULL;
-        acpi_status status;
         int type;
         unsigned long long sta;
+        struct acpi_device *device;
+        acpi_status status;
         int result;
 
         result = acpi_bus_type_and_status(handle, &type, &sta);
@@ -1414,13 +1414,16 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl,
             !(sta & ACPI_STA_DEVICE_FUNCTIONING))
                 return AE_CTRL_DEPTH;
 
-        if (ops->acpi_op_add)
-                status = acpi_add_single_object(&device, handle, type, sta,
-                                                ops);
-        else
-                status = acpi_bus_get_device(handle, &device);
+        /*
+         * We may already have an acpi_device from a previous enumeration.  If
+         * so, we needn't add it again, but we may still have to start it.
+         */
+        device = NULL;
+        acpi_bus_get_device(handle, &device);
+        if (ops->acpi_op_add && !device)
+                acpi_add_single_object(&device, handle, type, sta, ops);
 
-        if (ACPI_FAILURE(status))
+        if (!device)
                 return AE_CTRL_DEPTH;
 
         if (ops->acpi_op_start && !(ops->acpi_op_add)) {