time: Add mechanism to recognize clocksource in time_get_snapshot

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System time snapshots are not conveying information about the current
clocksource which was used, but callers like the PTP KVM guest
implementation have the requirement to evaluate the clocksource type to
select the appropriate mechanism.

Introduce a clocksource id field in struct clocksource which is by default
set to CSID_GENERIC (0). Clocksource implementations can set that field to
a value which allows to identify the clocksource.

Store the clocksource id of the current clocksource in the
system_time_snapshot so callers can evaluate which clocksource was used to
take the snapshot and act accordingly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-5-jianyong.wu@arm.com

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Thomas Gleixner 2020-12-09 14:09:27 +08:00 • committed by Marc Zyngier

parent a8cf291bda

commit b2c67cbe9f

5 changed files with 27 additions and 5 deletions

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6

include/linux/clocksource.h

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11

include/linux/clocksource_ids.h

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12

include/linux/timekeeping.h

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