Messages in this thread | | | Subject | Re: [RFC 1/2] PM / suspend: Add platform_suspend_target_state() | From | Florian Fainelli <> | Date | Wed, 12 Jul 2017 11:08:19 -0700 |
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On 06/29/2017 04:00 PM, Rafael J. Wysocki wrote: > On Thursday, June 22, 2017 06:08:36 PM Florian Fainelli wrote: >> Add an optional platform_suspend_ops callback: target_state, and a >> helper function globally visible to get this called: >> platform_suspend_target_state(). >> >> This is useful for platform specific drivers that may need to take a >> slightly different suspend/resume path based on the system's >> suspend/resume state being entered. >> >> Although this callback is optional and documented as such, it requires >> a platform_suspend_ops::begin callback to be implemented in order to >> provide an accurate suspend/resume state within the driver that >> implements this platform_suspend_ops. >> >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> >> --- >> include/linux/suspend.h | 12 ++++++++++++ >> kernel/power/suspend.c | 15 +++++++++++++++ >> 2 files changed, 27 insertions(+) >> >> diff --git a/include/linux/suspend.h b/include/linux/suspend.h >> index d9718378a8be..d998a04a90a2 100644 >> --- a/include/linux/suspend.h >> +++ b/include/linux/suspend.h >> @@ -172,6 +172,15 @@ static inline void dpm_save_failed_step(enum suspend_stat_step step) >> * Called by the PM core if the suspending of devices fails. >> * This callback is optional and should only be implemented by platforms >> * which require special recovery actions in that situation. >> + * >> + * @target_state: Returns the suspend state the suspend_ops will be entering. >> + * Called by device drivers that need to know the platform specific suspend >> + * state the system is about to enter. >> + * This callback is optional and should only be implemented by platforms >> + * which require special handling of power management states within >> + * drivers. It does require @begin to be implemented to provide the suspend >> + * state. Return value is platform_suspend_ops specific, and may be a 1:1 >> + * mapping to suspend_state_t when relevant. >> */ >> struct platform_suspend_ops { >> int (*valid)(suspend_state_t state); >> @@ -184,6 +193,7 @@ struct platform_suspend_ops { >> bool (*suspend_again)(void); >> void (*end)(void); >> void (*recover)(void); >> + int (*target_state)(void); > > I would use unsigned int (the sign should not matter). > >> }; > > That's almost what I was thinking about except that the values returned by > ->target_state should be unique, so it would be good to do something to > ensure that. > > The concern is as follows. > > Say you have a driver develped for platform X where ->target_state returns > A for "mem" and B for "standby". Then, the same IP is re-used on platform Y > returning B for "mem" and C for "standby" and now the driver cannot > distinguish between them. > > Moreover, even if they both returned A for "mem" there might be differences > in how "mem" was defined by each of them and therefore in what the driver was > expected to do to handle "mem" on X and Y.
That makes sense, would you need the core implementation in platform_suspend_target_state() to range check what suspend_ops->target_state() returns against a set of reserved value say, checking from 0 up to ACPI_S_STATE_COUNT or is there another range you would like to see being used?
Thanks! -- Florian
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