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timekeeping: Add clocksource ID to struct system_counterval_t

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Clocksource pointers can be problematic to obtain for drivers which are not
clocksource drivers themselves. In particular, the RFC virtio_rtc driver
[1] would require a new helper function to obtain a pointer to the ARM
Generic Timer clocksource. The ptp_kvm driver also required a similar
workaround.

Add a clocksource ID member to struct system_counterval_t, which in the
future shall identify the clocksource, and which shall replace the struct
clocksource * member. By this, get_device_system_crosststamp() callers
(such as virtio_rtc and ptp_kvm) will be able to supply easily accessible
clocksource ids instead of clocksource pointers.

[1] https://lore.kernel.org/lkml/20231218073849.35294-1-peter.hilber@opensynergy.com/

Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240201010453.2212371-3-peter.hilber@opensynergy.com
This commit is contained in:
Peter Hilber 2024-02-01 02:04:47 +01:00 committed by Thomas Gleixner
parent c55cbfcea6
commit 93630d6df7
1 changed files with 5 additions and 0 deletions
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5
include/linux/timekeeping.h
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@ -273,10 +273,15 @@ struct system_device_crosststamp {
* @cycles: System counter value
* @cs: Clocksource corresponding to system counter value. Used by
* timekeeping code to verify comparibility of two cycle values
* @cs_id: Clocksource ID corresponding to system counter value. To be
* used instead of cs in the future.
* The default ID, CSID_GENERIC, does not identify a specific
* clocksource.
*/
struct system_counterval_t {
u64 cycles;
struct clocksource *cs;
enum clocksource_ids cs_id;
};
/*