diff options
| author | Babis Chalios <bchalios@amazon.es> | 2026-01-30 17:36:01 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-02-02 18:06:00 -0800 |
| commit | 3b1526ddb25452385b52f2588b655f524a57070b (patch) | |
| tree | 7fb5eac20cb7b2b5041a724d7802ac339fb71338 /include/uapi/linux | |
| parent | 3495064b6d65a669b409cfe1241db4f3c540251a (diff) | |
ptp: vmclock: support device notifications
Add optional support for device notifications in VMClock. When
supported, the hypervisor will send a device notification every time it
updates the seq_count to a new even value.
Moreover, add support for poll() in VMClock as a means to propagate this
notification to user space. poll() will return a POLLIN event to
listeners every time seq_count changes to a value different than the one
last seen (since open() or last read()/pread()). This means that when
poll() returns a POLLIN event, listeners need to use read() to observe
what has changed and update the reader's view of seq_count. In other
words, after a poll() returned, all subsequent calls to poll() will
immediately return with a POLLIN event until the listener calls read().
The device advertises support for the notification mechanism by setting
flag VMCLOCK_FLAG_NOTIFICATION_PRESENT in vmclock_abi flags field. If
the flag is not present the driver won't setup the ACPI notification
handler and poll() will always immediately return POLLHUP.
Signed-off-by: Babis Chalios <bchalios@amazon.es>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Takahiro Itazuri <itazur@amazon.com>
Link: https://patch.msgid.link/20260130173704.12575-3-itazur@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/uapi/linux')
| -rw-r--r-- | include/uapi/linux/vmclock-abi.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/uapi/linux/vmclock-abi.h b/include/uapi/linux/vmclock-abi.h index 937fe00e4f33..d320623b0118 100644 --- a/include/uapi/linux/vmclock-abi.h +++ b/include/uapi/linux/vmclock-abi.h @@ -121,6 +121,11 @@ struct vmclock_abi { * loaded from some save state (restored from a snapshot). */ #define VMCLOCK_FLAG_VM_GEN_COUNTER_PRESENT (1 << 8) + /* + * If the NOTIFICATION_PRESENT flag is set, the hypervisor will send + * a notification every time it updates seq_count to a new even number. + */ +#define VMCLOCK_FLAG_NOTIFICATION_PRESENT (1 << 9) __u8 pad[2]; __u8 clock_status; |