18fd456ecSSaravana KannanWhat: /sys/devices/.../state_synced 28fd456ecSSaravana KannanDate: May 2020 38fd456ecSSaravana KannanContact: Saravana Kannan <saravanak@google.com> 48fd456ecSSaravana KannanDescription: 58fd456ecSSaravana Kannan The /sys/devices/.../state_synced attribute is only present for 68fd456ecSSaravana Kannan devices whose bus types or driver provides the .sync_state() 78fd456ecSSaravana Kannan callback. The number read from it (0 or 1) reflects the value 88fd456ecSSaravana Kannan of the device's 'state_synced' field. A value of 0 means the 98fd456ecSSaravana Kannan .sync_state() callback hasn't been called yet. A value of 1 108fd456ecSSaravana Kannan means the .sync_state() callback has been called. 118fd456ecSSaravana Kannan 128fd456ecSSaravana Kannan Generally, if a device has sync_state() support and has some of 138fd456ecSSaravana Kannan the resources it provides enabled at the time the kernel starts 148fd456ecSSaravana Kannan (Eg: enabled by hardware reset or bootloader or anything that 158fd456ecSSaravana Kannan run before the kernel starts), then it'll keep those resources 168fd456ecSSaravana Kannan enabled and in a state that's compatible with the state they 178fd456ecSSaravana Kannan were in at the start of the kernel. The device will stop doing 188fd456ecSSaravana Kannan this only when the sync_state() callback has been called -- 198fd456ecSSaravana Kannan which happens only when all its consumer devices are registered 208fd456ecSSaravana Kannan and have probed successfully. Resources that were left disabled 218fd456ecSSaravana Kannan at the time the kernel starts are not affected or limited in 228fd456ecSSaravana Kannan any way by sync_state() callbacks. 238fd456ecSSaravana Kannan 248fd456ecSSaravana Kannan 25