On Mon, 8 Feb 2016, Rafael J. Wysocki wrote: > On Monday, February 08, 2016 10:57:01 AM Stefano Stabellini wrote: > > On Sat, 6 Feb 2016, Rafael J. Wysocki wrote: > > > On Fri, Feb 5, 2016 at 4:05 AM, Shannon Zhao <zhaoshenglong@xxxxxxxxxx> wrote: > > > > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx> > > > > > > > > ACPI 6.0 introduces a new table STAO to list the devices which are used > > > > by Xen and can't be used by Dom0. On Xen virtual platforms, the physical > > > > UART is used by Xen. So here it hides UART from Dom0. > > > > > > > > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx> > > > > Reviewed-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> > > > > > > Well, this doesn't look right to me. > > > > > > We need to find a nicer way to achieve what you want. > > > > I take that you are talking about how to honor the STAO table in Linux. > > Do you have any concrete suggestions? > > I do. > > The last hunk of the patch is likely what it needs to be, although I'm > not sure if the place it is added to is the right one. That's a minor thing, > though. > > The other part is problematic. Not that as it doesn't work, but because of > how it works. With these changes the device will be visible to the OS (in > fact to user space even), but will never be "present". I'm not sure if > that's what you want? > > It might be better to add a check to acpi_bus_type_and_status() that will > evaluate the "should ignore?" thing and return -ENODEV if this is true. This > way the device won't be visible at all. Something like below? Actually your suggestion is better, thank you! diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index 78d5f02..4778c51 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -1455,6 +1455,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type, if (ACPI_FAILURE(status)) return -ENODEV; + if (acpi_check_device_is_ignored(handle)) + return -ENODEV; + switch (acpi_type) { case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */ case ACPI_TYPE_DEVICE: -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html