On Tue, May 26, 2020 at 09:24:39PM -0400, Andrew F. Davis wrote: > On 5/25/20 10:11 AM, Krzysztof Kozlowski wrote: > > All battery related data could be important for user-space. For example > > time-to-full could be shown to user on the screen or health could be > > monitored for any issues. Instead of comparing few selected old/new > > values, just check if anything changed in the cache. > > > > > At least some value will change every time we poll the battery, are we > okay with having power_supply_changed() called every time?
Hi, Let me give few arguments: 1. "Every time" means still once per poll interval or in case of many get_property() calls, once per 5 seconds. In first case, if users sets polling every 1 second, I expect he knows what he wants. I2C will be busy anyway so uevents should not matter that much. In second case, called through get_property(), once per 5 seconds is not that frequent. 2. Different drivers do it differently. Many chargers notify about everything. Most fuel gauges only on status or capacity change (although I am not sure if they measure more) but few FG send uevents about everything (max17042_battery, sbs-battery, s3c_adc_battery). 3. If drivers does not send notifications on changed properties of battery, then basically the user-space has to poll every time for all data which is not being a trigger. The overhead for system would be the same, I guess. Best regards, Krzysztof > Andrew > > > > Signed-off-by: Krzysztof Kozlowski <[email protected]> > > --- > > drivers/power/supply/bq27xxx_battery.c | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/power/supply/bq27xxx_battery.c > > b/drivers/power/supply/bq27xxx_battery.c > > index 942c92127b6d..33c26d42cd02 100644 > > --- a/drivers/power/supply/bq27xxx_battery.c > > +++ b/drivers/power/supply/bq27xxx_battery.c > > @@ -1612,12 +1612,10 @@ void bq27xxx_battery_update(struct > > bq27xxx_device_info *di) > > di->charge_design_full = bq27xxx_battery_read_dcap(di); > > } > > > > - if ((di->cache.capacity != cache.capacity) || > > - (di->cache.flags != cache.flags)) > > + if (memcmp(&di->cache, &cache, sizeof(cache)) != 0) { > > power_supply_changed(di->bat); > > - > > - if (memcmp(&di->cache, &cache, sizeof(cache)) != 0) > > di->cache = cache; > > + } > > > > di->last_update = jiffies; > > } > >
