ptp: Remove 'default y' for VMCLOCK PTP device

The VMCLOCK device gives support for accurate timekeeping even across
live migration, unlike the KVM PTP clock. To help ensure that users can
always use ptp_vmclock where it's available in preference to ptp_kvm,
set it to 'default PTP_1588_CLOCK_VMCLOCK' instead of 'default y'.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index e98c9767e0efd675d2db5f30dc06a29cc2808a8f..ed087ae75f0ede6f2410824a88cde3539d6a478d 100644 (file)
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -135,12 +135,16 @@ config PTP_1588_CLOCK_VMCLOCK
        tristate "Virtual machine PTP clock"
        depends on X86_TSC || ARM_ARCH_TIMER
        depends on PTP_1588_CLOCK && ACPI && ARCH_SUPPORTS_INT128
-       default y
+       default PTP_1588_CLOCK_KVM
        help
          This driver adds support for using a virtual precision clock
          advertised by the hypervisor. This clock is only useful in virtual
          machines where such a device is present.
 
+         Unlike the KVM virtual PTP clock, the VMCLOCK device offers support
+         for reliable timekeeping even across live migration. So this driver
+         is enabled by default whenever the KVM PTP clock is.
+
          To compile this driver as a module, choose M here: the module
          will be called ptp_vmclock.