Messages in this thread Patch in this message | | | Date | Thu, 4 Sep 2008 13:40:58 -0600 | From | Michal Hocko <> | Subject | Re: Why is /sys/class/power_supply/CMB1/energy_now not exported? |
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On Mon, Jul 21, 2008 at 09:04:13PM -0600, Michal Hocko wrote: > [fixing bad linux kernel mailing list email address - sorry, but gmail's > thrown mailing delivery error to the spam] > > On Tue, Jul 22, 2008 at 01:03:11AM +0400, Alexey Starikovskiy wrote: > > Hi Michal, > > Hi Alexey, > > > > > the charge_now part of your patch seems to be correct, but the > > calculation is somehow broken -- > > I have made some experiments and the result is quite surprising to me. > It seems that this problem is somehow related to Debian distribution > kernel, because I wasn't able to reproduce it with the Vanilla kernel (I > had to screw something up last time when I have checked that and > reported in the original message). > > I have tried 3 configurations: > * 2.6.25 - Vanilla kernel with config-2.6.25 config and result output in > powertop-2.6.25-good > * 2.6.25-2 - Debian distribution kernel with config-2.6.25-2 config and > powertop-2.6.25-2-bad output > * 2.6.26 - Vanilla kernel with config-2.6.26 config and result output in > powertop-2.6.26-good [...]
I had some time to get back to this issue and the problem why I have seen different behavior on distribution and vanilla kernel was in configuration. While distribution kernel doesn't use CONFIG_ACPI_PROCFS_POWER=y while my vanilla kernel configuration does! This means that the patched code wasn't triggered in my vanilla kernel testing.
So that I have checked the print_batter_sysfs again and it seems that the problem is on another place: powertop.c:648 sprintf(filename, "/sys/class/power_supply/%s/current_now", dirent->d_name); file = fopen(filename, "r"); if (!file) continue; memset(line, 0, 1024); if (fgets(line, 1024, file) != NULL) { watts_drawn = strtoull(line, NULL, 10) / 1000000.0; } fclose(file);
if (!dontcount) { rate += watts_drawn + voltage * amperes_drawn; }
current rate (later used for the remaining time calculation: display.c:201 sprintf(buffer, _("Power usage (ACPI estimate): %3.1fW (%3.1f hours)"), rate, cap/rate); )
is calculated as watts_drawn + voltage which is not correct, because current_* values are in A and not in W (according to linux-src/Documentation/power/power_supply_class.txt).
Updated patch is attached. This one is already working for me.
-- Michal Hocko From: mstsxfx@gmail.com Subject: [PATCH] use charge_now when energy_now is not present
Some batteries (like one in the Futjitsu Siemens Lifebook S71110) don't export energy_now attribute and exports only change_now in the power_supply sys directory. However, we can use this value when it is multiplied by current voltage.
In addition, /sys/class/power_supply/*/current_* are in ľA according to the linux-src/Documentation/power/power_supply_class.txt and not in ľW as expected by the original code
Signed-off-by: Michal Hocko <mstsxfx@gmail.com>
Index: powertop/powertop.c =================================================================== --- powertop.orig/powertop.c 2008-09-01 14:19:21.000000000 -0600 +++ powertop/powertop.c 2008-09-01 14:27:07.000000000 -0600 @@ -630,12 +630,19 @@ void print_battery_sysfs(void) sprintf(filename, "/sys/class/power_supply/%s/energy_now", dirent->d_name); file = fopen(filename, "r"); - if (!file) - continue; - memset(line, 0, 1024); - if (fgets(line, 1024, file) != NULL) { - watts_left = strtoull(line, NULL, 10) / 1000000.0; + watts_left = 1; + if (!file) { + sprintf(filename, "/sys/class/power_supply/%s/charge_now", dirent->d_name); + file = fopen(filename, "r"); + if (!file) + continue; + + /* W = A * V */ + watts_left = voltage; } + memset(line, 0, 1024); + if (fgets(line, 1024, file) != NULL) + watts_left *= strtoull(line, NULL, 10) / 1000000.0; fclose(file); sprintf(filename, "/sys/class/power_supply/%s/current_now", dirent->d_name); @@ -644,7 +651,7 @@ void print_battery_sysfs(void) continue; memset(line, 0, 1024); if (fgets(line, 1024, file) != NULL) { - watts_drawn = strtoull(line, NULL, 10) / 1000000.0; + amperes_drawn = strtoull(line, NULL, 10) / 1000000.0; } fclose(file); | |