ACPI/PCI: Do not preserve _OSC control bits returned by a query

There is the assumption in acpi_pci_osc_control_set() that it is
always sufficient to compare the mask of _OSC control bits to be
requested with the result of an _OSC query where all of the known
control bits have been checked.  However, in general, that need not
be the case.  For example, if an _OSC feature A depends on an _OSC
feature B and control of A, B plus another _OSC feature C is
requested simultaneously, the BIOS may return A, B, C, while it would
only return C if A and C were requested without B.

That may result in passing a wrong mask of _OSC control bits to an
_OSC control request, in which case the BIOS may only grant control
of a subset of the requested features.  Moreover, acpi_pci_run_osc()
will return error code if that happens and the caller of
acpi_pci_osc_control_set() will not know that it's been granted
control of some _OSC features.  Consequently, the system will
generally not work as expected.

Apart from this acpi_pci_osc_control_set() always uses the mask
of _OSC control bits returned by the very first invocation of
acpi_pci_query_osc(), but that is done with the second argument
equal to OSC_PCI_SEGMENT_GROUPS_SUPPORT which generally happens
to affect the returned _OSC control bits.

For these reasons, make acpi_pci_osc_control_set() always check if
control of the requested _OSC features will be granted before making
the final control request.  As a result, the osc_control_qry and
osc_queried members of struct acpi_pci_root are not necessary any
more, so drop them and remove the remaining code referring to them.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index d2ae816df0f5fb31ec0ad853b73a0fc5662e07b5..77cd19697b1e9f25a0dc1f64218cf5e37622bdb5 100644 (file)
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -249,12 +249,8 @@ static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
        status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
        if (ACPI_SUCCESS(status)) {
                root->osc_support_set = support;
-               if (control) {
+               if (control)
                        *control = result;
-               } else {
-                       root->osc_control_qry = result;
-                       root->osc_queried = 1;
-               }
        }
        return status;
 }
@@ -409,14 +405,12 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 flags)
                goto out;
 
        /* Need to query controls first before requesting them */
-       if (!root->osc_queried) {
-               status = acpi_pci_query_osc(root, root->osc_support_set, NULL);
-               if (ACPI_FAILURE(status))
-                       goto out;
-       }
-       if ((root->osc_control_qry & control_req) != control_req) {
-               printk(KERN_DEBUG
-                      "Firmware did not grant requested _OSC control\n");
+       flags = control_req;
+       status = acpi_pci_query_osc(root, root->osc_support_set, &flags);
+       if (ACPI_FAILURE(status))
+               goto out;
+
+       if (flags != control_req) {
                status = AE_SUPPORT;
                goto out;
        }

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index baacd98e7cc6244b795b5db1b09b440292ee3dac..4de84ce3a927123f118861df950202a8dba1a536 100644 (file)
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -377,9 +377,6 @@ struct acpi_pci_root {
 
        u32 osc_support_set;    /* _OSC state of support bits */
        u32 osc_control_set;    /* _OSC state of control bits */
-       u32 osc_control_qry;    /* the latest _OSC query result */
-
-       u32 osc_queried:1;      /* has _OSC control been queried? */
 };
 
 /* helper */