| Message ID | 20200525141200.17199-1-krzk@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | [1/2] power: supply: bq27xxx_battery: Notify about all battery changes | expand |
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? Andrew > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org> > --- > 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; > } >
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 <krzk@kernel.org> > > --- > > 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; > > } > >
On Wed, May 27, 2020 at 09:22:24AM +0200, Krzysztof Kozlowski wrote: > 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. > And one more: 4. I actually needed for my project. I have a user-space which previously was polling the battery status but I converted it to udev events. The voltage, current and temperature are important for me as well so I need all uevents. Best regards, Krzysztof
On Tue 2020-05-26 21:24:39, 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? I believe that's very bad idea. AFAICT that would wake up userspace every 5 seconds, eating power in unexpected way, and without easy ability of opting out. IOW a regression. Pavel
On Tue, Jun 16, 2020 at 12:52:24PM +0200, Pavel Machek wrote: > On Tue 2020-05-26 21:24:39, 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? > > I believe that's very bad idea. AFAICT that would wake up userspace every > 5 seconds, eating power in unexpected way, and without easy ability of opting > out. IOW a regression. It won't be 5 seconds but poll_interval which is 360 seconds by default. It can be 5 seconds if user-space changes this time or if user-space keeps asking for get_property. In first case: user-space kind of decided about it... In second: user-space is already woken-up since it polls get properties. However I understand that this is quite intrusive change and maybe in such case user-space should just keep polling (if it wants all data to be provided every n-seconds). Best regards, Krzysztof
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; }
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. Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org> --- drivers/power/supply/bq27xxx_battery.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)