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author | Rafael J. Wysocki <rjw@sisk.pl> | 2010-08-23 21:55:59 (GMT) |
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committer | Jesse Barnes <jbarnes@virtuousgeek.org> | 2010-08-24 20:44:17 (GMT) |
commit | 2b8fd9186d9275b07aef43e5bb4e98cd571f9a7d (patch) | |
tree | 8ddae8c12e8dabfffb3eed75aff0f3121b955e9c /drivers | |
parent | ab8e8957a2ae21c0f036476c6db13e949be730ac (diff) | |
download | linux-2b8fd9186d9275b07aef43e5bb4e98cd571f9a7d.tar.xz |
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>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/acpi/pci_root.c | 20 |
1 files changed, 7 insertions, 13 deletions
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c index d2ae816..77cd196 100644 --- 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; } |