On Wed, Oct 29, 2014 at 02:35:26PM +0100, Johan Hovold wrote: > On Wed, Oct 29, 2014 at 06:20:40AM -0700, Guenter Roeck wrote: > > On 10/29/2014 05:34 AM, Johan Hovold wrote: > > > On Tue, Oct 28, 2014 at 03:16:10PM +0000, Russell King - ARM Linux wrote: > > >> On Tue, Oct 28, 2014 at 02:12:57PM +0100, Johan Hovold wrote: > > >>> That's not what I was trying to refer to. But the patch set explicitly > > >>> allows for multiple, prioritised power-off handlers, which can power > > >>> off a board in different ways and with various degrees of success. > > >>> Specifically, it allows for fallback handlers in case one or more > > >>> power-off handlers fail. > > >>> > > >>> So if we allow for that, what is to prevent the final power-off handler > > >>> from failing? And should this not be logged by arch code in the same way > > >>> as failure to restart is? > > >> > > >> And how is that different from having a set of power-off handlers, and > > >> reporting when each individual one fails? Don't you want to know if > > >> your primary high priority reboot handler fails, just as much as you > > >> want to know if your final last-resort power-off handler fails? > > > > > > Good point. Failed power-off should probably be logged by the power-off > > > call chain implementation (which seems to makes notifier chains a bad > > > fit). > > > > Good that I just replaced notifier chain with an open coded implementation. > > Good to hear. > > > Sure, that is possible, but I would prefer to do that as a follow-up commit, > > and it should be discussed in the context of the power-off handler patch set. > > Fine with me. > > > > And what about any power-off latencies? Should this always be dealt with > > > in the power-off handler? > > > > > > Again, if it's predictable and high, as in the OMAP RTC case, it should > > > go in the handler. But what if it's just normal bus latencies > > > (peripheral busses, i2c, or whatever people may come up with)? > > > > > > Should there always be a short delay before calling the next handler? > > > > That delay would depend on the individual power-off handler, so I think > > the current implementation works just fine (where power-off handlers > > implement the delay). > > Some don't, and could possibly unknowingly have been relying on the fact > that they could return to user space and be powered off at some later > time. With systemd that would have caused a panic. > Agreed, but there are two cases to consider: What should be the delay before the next power-off handler is called, and what should the system do if all power-off handlers fail (or if there are none). The current behavior isn't exactly well defined. Ok, with systemd that results in a crash, but I am not really sure if one can or should blame systemd for that. The discussion about systemd and its philosophy should not cloud the fact that power-off behavior isn't exactly well defined. > Also consider generic power-off handlers such as gpio-poweroff. It > currently hard-codes a three-second delay but the actual delay would > really be board specific. > A configurable delay would address that. The actually required delay could be provided in platform data or as devicetree property. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
