On Thu, Jun 18, 2015 at 3:04 AM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote: > On 10/06/2014 10:28 PM, Guenter Roeck wrote: >> Various drivers implement architecture and/or device specific means to >> remove power from the system. For the most part, those drivers set the >> global variable pm_power_off to point to a function within the driver. >> >> This mechanism has a number of drawbacks. Typically only one scheme >> to remove power is supported (at least if pm_power_off is used). >> At least in theory there can be multiple means remove power, some of >> which may be less desirable. For example, some mechanisms may only >> power off the CPU or the CPU card, while another may power off the >> entire system. Others may really just execute a restart sequence >> or drop into the ROM monitor. Using pm_power_off can also be racy >> if the function pointer is set from a driver built as module, as the >> driver may be in the process of being unloaded when pm_power_off is >> called. If there are multiple poweroff handlers in the system, removing >> a module with such a handler may inadvertently reset the pointer to >> pm_power_off to NULL, leaving the system with no means to remove power. >> >> Introduce a system poweroff handler call chain to solve the described >> problems. This call chain is expected to be executed from the >> architecture specific machine_power_off() function. Drivers providing >> system poweroff functionality are expected to register with this call chain. >> By using the priority field in the notifier block, callers can control >> poweroff handler execution sequence and thus ensure that the poweroff >> handler with the optimal capabilities to remove power for a given system >> is called first. > > What happened to this series? I want to add shutdown support to my > platform and I need to write a register on the PMIC in one driver to > configure it for shutdown instead of restart and then write an MMIO > register to tell the PMIC to actually do the shutdown in another driver. > It seems that the notifier solves this case for me, albeit with the > slight complication that I need to order the two with some priority. I was wondering the same thing. I did find out that things kind of stalled after Linus cast doubt on the chosen path [1]. I'm not sure there's any consensus on what would be best to do instead. Frans [1] https://lkml.org/lkml/2014/11/6/641
