From 2b8fd9186d9275b07aef43e5bb4e98cd571f9a7d Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 23 Aug 2010 23:55:59 +0200 Subject: 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 Signed-off-by: Jesse Barnes --- drivers/acpi/pci_root.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) (limited to 'drivers') diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c index d2ae816df0f5..77cd19697b1e 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; } -- cgit v1.2.3