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| author | Saravana Kannan <saravanak@google.com> | 2020-05-21 22:17:59 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-07-10 16:24:56 +0300 |
| commit | 8fd456ec0cf03875908d6b67c1cd20cf0a7b4474 (patch) | |
| tree | 553496d0bbead2370f0eb1510a92db046bc9df9e /Documentation/ABI | |
| parent | 287905e68dd29873bcb7986a8290cd1e4cfde600 (diff) | |
| download | linux-8fd456ec0cf03875908d6b67c1cd20cf0a7b4474.tar.xz | |
driver core: Add state_synced sysfs file for devices that support it
This can be used to check if a device supports sync_state() callbacks
and therefore keeps resources left on by the bootloader enabled till all
its consumers have probed.
This can also be used to check if sync_state() has been called for a
device or whether it is still trying to keep resources enabled because
they were left enabled by the bootloader and all its consumers haven't
probed yet.
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200521191800.136035-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-devices-state_synced | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-state_synced b/Documentation/ABI/testing/sysfs-devices-state_synced new file mode 100644 index 000000000000..0c922d7d02fc --- /dev/null +++ b/Documentation/ABI/testing/sysfs-devices-state_synced @@ -0,0 +1,24 @@ +What: /sys/devices/.../state_synced +Date: May 2020 +Contact: Saravana Kannan <saravanak@google.com> +Description: + The /sys/devices/.../state_synced attribute is only present for + devices whose bus types or driver provides the .sync_state() + callback. The number read from it (0 or 1) reflects the value + of the device's 'state_synced' field. A value of 0 means the + .sync_state() callback hasn't been called yet. A value of 1 + means the .sync_state() callback has been called. + + Generally, if a device has sync_state() support and has some of + the resources it provides enabled at the time the kernel starts + (Eg: enabled by hardware reset or bootloader or anything that + run before the kernel starts), then it'll keep those resources + enabled and in a state that's compatible with the state they + were in at the start of the kernel. The device will stop doing + this only when the sync_state() callback has been called -- + which happens only when all its consumer devices are registered + and have probed successfully. Resources that were left disabled + at the time the kernel starts are not affected or limited in + any way by sync_state() callbacks. + + |