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

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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>
This commit is contained in:
Rafael J. Wysocki 2010-08-23 23:55:59 +02:00 committed by Jesse Barnes
parent ab8e8957a2
commit 2b8fd9186d
2 changed files with 7 additions and 16 deletions
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20
drivers/acpi/pci_root.c
View file

@ -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;
}

3
include/acpi/acpi_bus.h
View file

@ -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 */