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From: Sebastian R. <sr...@ke...> - 2020-07-25 19:01:04
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Hi, On Wed, Jun 24, 2020 at 01:42:26AM +0200, Kristian Klausen wrote: > On 07.02.2018 15.58, Ognjen Galic wrote: > > This is a patch that implements a generic hooking API for the > > generic ACPI battery driver. > > > > With this new generic API, drivers can expose platform specific > > behaviour via sysfs attributes in /sys/class/power_supply/BATn/ > > in a generic way. > > > > A perfect example of the need for this API are Lenovo ThinkPads. > > > > Lenovo ThinkPads have a ACPI extension that allows the setting of > > start and stop charge thresholds in the EC and battery firmware > > via ACPI. The thinkpad_acpi module can use this API to expose > > sysfs attributes that it controls inside the ACPI battery driver > > sysfs tree, under /sys/class/power_supply/BATN/. > > > > The file drivers/acpi/battery.h has been moved to > > include/acpi/battery.h and the includes inside ac.c, sbs.c, and > > battery.c have been adjusted to reflect that. > > > > When drivers hooks into the API, the API calls add_battery() for > > each battery in the system that passes it a acpi_battery > > struct. Then, the drivers can use device_create_file() to create > > new sysfs attributes with that struct and identify the batteries > > for per-battery attributes. > > Hi > > I did that, when I implemented charge threshold support for ASUS > laptops[1][2]. > > It works very well but I can't control the threshold with udev (also > reported by another user here[3]). So I did a bit of digging and the doc[4] > states: "If attributes are added after the device is registered, then > userspace won’t get notified and userspace will not know about the new > attributes.", which seems to be the way the current code works: > power_supply_register_no_ws is called[5] and if it success all the hooks are > run. > > Looking at the code I'm not sure there is a easy way to fix it, do you have > any good ideas? That problem is described by Greg in his blog post from 2013: http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/ The power-supply subsystem offers registering extra attributes at registration time by filling in the .attr_grp field in the struct power_supply_config supplied as last parameter to power_supply_register_*() since 4.21. -- Sebastian |
