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Commit 2b8fd918 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki Committed by Jesse Barnes
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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: default avatarRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent ab8e8957
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+7 −13
Original line number Diff line number Diff line
@@ -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);
	flags = control_req;
	status = acpi_pci_query_osc(root, root->osc_support_set, &flags);
	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");

	if (flags != control_req) {
		status = AE_SUPPORT;
		goto out;
	}
+0 −3
Original line number Diff line number Diff line
@@ -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 */