ACPI: fix a regression of ACPI device driver autoloading

commit 3620f2f2f39e7870cf1a4fb2e34063a142f28716 sets the cid of
ACPI video/dock/bay device and leaves the hid empty.
As a result, "modalias" should export the cid for
devices which don't have a hid.

ACPI Video driver is not autoloaded with
commit 3620f2f2f39e7870cf1a4fb2e34063a142f28716 applied.
"cat /sys/.../device:03(acpi video bus)/modalias" shows nothing.

ACPI Video driver is autoloaded after revert that commit.
"cat /sys/.../LNXVIDEO:0x/modalias" shows "acpi:LNXVIDEO:"

ACPI Video driver is autoloaded with commit
3620f2f2f39e7870cf1a4fb2e34063a142f28716 and this patch applied.
"cat /sys/.../device:03(acpi video bus)/modalias"
shows "acpi:LNXVIDEO:"

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 57570ac4780..e6ce262b5d4 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -39,20 +39,26 @@ static int create_modalias(struct acpi_device *acpi_dev, char *modalias,
                            int size)
 {
         int len;
+        int count;
 
-        if (!acpi_dev->flags.hardware_id)
+        if (!acpi_dev->flags.hardware_id && !acpi_dev->flags.compatible_ids)
                 return -ENODEV;
 
-        len = snprintf(modalias, size, "acpi:%s:",
-                       acpi_dev->pnp.hardware_id);
-        if (len < 0 || len >= size)
-                return -EINVAL;
+        len = snprintf(modalias, size, "acpi:");
         size -= len;
 
+        if (acpi_dev->flags.hardware_id) {
+                count = snprintf(&modalias[len], size, "%s:",
+                                 acpi_dev->pnp.hardware_id);
+                if (count < 0 || count >= size)
+                        return -EINVAL;
+                len += count;
+                size -= count;
+        }
+
         if (acpi_dev->flags.compatible_ids) {
                 struct acpi_compatible_id_list *cid_list;
                 int i;
-                int count;
 
                 cid_list = acpi_dev->pnp.cid_list;
                 for (i = 0; i < cid_list->count; i++) {