Hi Guenter,
On Sun, Mar 3, 2019 at 5:13 PM Guenter Roeck <gro...@google.com> wrote: > > On Sun, Mar 3, 2019 at 4:54 PM RaviChandra Sadineni > <ravisadin...@chromium.org> wrote: >> >> On chromebooks, power_manager daemon normally shutsdown(S5) the device >> when the battery charge falls below 4% threshold. Chromeos EC then >> normally spends an hour in S5 before hibernating. If the battery charge >> falls below critical threshold in the mean time, EC does a battery cutoff >> instead of hibernating. On some chromebooks, S5 is optimal enough >> resulting in EC hibernating without battery cut-off. This results in >> battery deep-discharging. This is a bad user experience as battery >> has to trickle charge before booting when the A.C is plugged in the next >> time. >> >> This patch exposes a sysfs file for an userland daemon to suggest EC if it >> has to do a battery cut-off instead of hibernating when the system enters >> S5 next time. >> >> Signed-off-by: RaviChandra Sadineni <ravisadin...@chromium.org> >> --- >> V2: Use kstrtobool() instead of kstrtou8() and add documentation. >> >> .../ABI/testing/sysfs-class-chromeos | 8 ++++ >> drivers/platform/chrome/cros_ec_sysfs.c | 37 +++++++++++++++++++ >> 2 files changed, 45 insertions(+) >> create mode 100644 Documentation/ABI/testing/sysfs-class-chromeos >> >> diff --git a/Documentation/ABI/testing/sysfs-class-chromeos >> b/Documentation/ABI/testing/sysfs-class-chromeos >> new file mode 100644 >> index 000000000000..44d3cee6e7ae >> --- /dev/null >> +++ b/Documentation/ABI/testing/sysfs-class-chromeos >> @@ -0,0 +1,8 @@ >> +What: /sys/class/chromeos/cros_ec/cutoff_at_shutdown >> +Date: February 2019 >> +Contact: Ravi Chandra Sadineni <ravisadin...@chromium.org> >> +Description: >> + On writing '[Yy1]' to cutoff_at_shutdown property, >> + kernel sends a host command to EC requesting battery >> + cutoff on next shutdown. If AC is plugged in before >> + next shutdown, EC resets this flag. >> diff --git a/drivers/platform/chrome/cros_ec_sysfs.c >> b/drivers/platform/chrome/cros_ec_sysfs.c >> index f34a50121064..f5168ce8bfc7 100644 >> --- a/drivers/platform/chrome/cros_ec_sysfs.c >> +++ b/drivers/platform/chrome/cros_ec_sysfs.c >> @@ -322,14 +322,51 @@ static ssize_t kb_wake_angle_store(struct device *dev, >> return count; >> } >> >> +/* Battery cut-off control */ >> +static ssize_t cutoff_at_shutdown_store(struct device *dev, >> + struct device_attribute *attr, >> + const char *buf, size_t count) >> +{ >> + struct ec_params_battery_cutoff *param; >> + struct cros_ec_command *msg; >> + int ret; >> + struct cros_ec_dev *ec = container_of( >> + dev, struct cros_ec_dev, class_dev); >> + bool cutoff_battery; >> + >> + if (kstrtobool(buf, &cutoff_battery)) >> + return -EINVAL; >> + >> + if (!cutoff_battery) >> + return count; >> + > > > It is quite unusual to only be able to set this option, but not to be able to > reset it. I think that warrants an explanation and reasoning. Also, if > clearing the flag is not supported, I would expect an attempt to do so to > return an error. There should also be an explanation in the code explaining > why the attribute is write-only. Added documentation for the reason behind making this flag write only. Instead of taking a boolean value, made this attribute more generic and took 'at-shutdown' as an option. This way it will be easy to extend this sysfs api in the future (if EC exposes more attributes for this host command). > > Guenter > >> >> + msg = kmalloc(sizeof(*msg) + EC_HOST_PARAM_SIZE, GFP_KERNEL); >> + if (!msg) >> + return -ENOMEM; >> + >> + param = (struct ec_params_battery_cutoff *)msg->data; >> + msg->command = EC_CMD_BATTERY_CUT_OFF + ec->cmd_offset; >> + msg->version = 1; >> + param->flags = EC_BATTERY_CUTOFF_FLAG_AT_SHUTDOWN; >> + msg->outsize = sizeof(*param); >> + msg->insize = 0; >> + ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg); >> + kfree(msg); >> + if (ret < 0) >> + return ret; >> + return count; >> +} >> + >> /* Module initialization */ >> >> static DEVICE_ATTR_RW(reboot); >> static DEVICE_ATTR_RO(version); >> static DEVICE_ATTR_RO(flashinfo); >> static DEVICE_ATTR_RW(kb_wake_angle); >> +static DEVICE_ATTR_WO(cutoff_at_shutdown); >> >> static struct attribute *__ec_attrs[] = { >> + &dev_attr_cutoff_battery_at_shutdown.attr, >> &dev_attr_kb_wake_angle.attr, >> &dev_attr_reboot.attr, >> &dev_attr_version.attr, >> -- >> 2.20.1 >> Thanks, Ravi