linux-kernel - Re: [PATCH v4 1/9] power: supply: sysfs: print single value in uevent for POWER_SUPPLY_PROP_CHARGE

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Message-ID: <e46c1453-6d47-489d-a5d1-1750d96139ad@weissschuh.net>
Date: Sun, 24 Nov 2024 18:55:31 +0100 (GMT+01:00)
From: Thomas Weißschuh <thomas@...ssschuh.net>
To: Armin Wolf <W_Armin@....de>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
	Sebastian Reichel <sre@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev
Subject: Re: [PATCH v4 1/9] power: supply: sysfs: print single value in
 uevent for POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR

Nov 24, 2024 18:47:39 Armin Wolf <W_Armin@....de>:

> Am 11.11.24 um 22:40 schrieb Thomas Weißschuh:
>
>> Currently an uevent contains the same string representation of a
>> property as sysfs. However for POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR this
>> is specially formatted to indicate all possible values.
>> This doesn't make sense for uevents and complicates parsing.
>> Instead only include the currently active value in uevents.
>>
>> As currently no in-tree driver uses POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR
>> this change is not a problem.
>> Soon the property will actually be used so fix the formatting before
>> that happens.
>
> AFAIK the cros-charge-behaviour driver does use POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR,
> so we have to make sure that no userspace application uses this uevent information.

It only does so after this series.
Currently it uses the ad-hoc sysfs attributes which don't show up in uevent.
(I'm the maintainer)

>
> Other than that:
>
> Reviewed-by: Armin Wolf <W_Armin@....de>

Thanks!

>
>> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
>> ---
>>   drivers/power/supply/power_supply_sysfs.c | 20 ++++++++++++++++----
>>   1 file changed, 16 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
>> index 571de43fcca9827cf0fe3023e453defbf1eaec7d..a7351b9c8fe34a464a4e69b1a1a4a4179c1a4b4f 100644
>> --- a/drivers/power/supply/power_supply_sysfs.c
>> +++ b/drivers/power/supply/power_supply_sysfs.c
>> @@ -268,9 +268,11 @@ static ssize_t power_supply_show_enum_with_available(
>>     return count;
>>   }
>>
>> -static ssize_t power_supply_show_property(struct device *dev,
>> -                     struct device_attribute *attr,
>> -                     char *buf) {
>> +static ssize_t power_supply_format_property(struct device *dev,
>> +                       bool uevent,
>> +                       struct device_attribute *attr,
>> +                       char *buf)
>> +{
>>     ssize_t ret;
>>     struct power_supply *psy = dev_get_drvdata(dev);
>>     const struct power_supply_attr *ps_attr = to_ps_attr(attr);
>> @@ -303,6 +305,8 @@ static ssize_t power_supply_show_property(struct device *dev,
>>                 psy->desc->usb_types, value.intval, buf);
>>         break;
>>     case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
>> +       if (uevent) /* no possible values in uevents */
>> +           goto default_format;
>>         ret = power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
>>                              value.intval, buf);
>>         break;
>> @@ -310,6 +314,7 @@ static ssize_t power_supply_show_property(struct device *dev,
>>         ret = sysfs_emit(buf, "%s\n", value.strval);
>>         break;
>>     default:
>> +default_format:
>>         if (ps_attr->text_values_len > 0 &&
>>                 value.intval < ps_attr->text_values_len && value.intval >= 0) {
>>             ret = sysfs_emit(buf, "%s\n", ps_attr->text_values[value.intval]);
>> @@ -321,6 +326,13 @@ static ssize_t power_supply_show_property(struct device *dev,
>>     return ret;
>>   }
>>
>> +static ssize_t power_supply_show_property(struct device *dev,
>> +                     struct device_attribute *attr,
>> +                     char *buf)
>> +{
>> +   return power_supply_format_property(dev, false, attr, buf);
>> +}
>> +
>>   static ssize_t power_supply_store_property(struct device *dev,
>>                        struct device_attribute *attr,
>>                        const char *buf, size_t count) {
>> @@ -437,7 +449,7 @@ static int add_prop_uevent(const struct device *dev, struct kobj_uevent_env *env
>>     pwr_attr = &power_supply_attrs[prop];
>>     dev_attr = &pwr_attr->dev_attr;
>>
>> -   ret = power_supply_show_property((struct device *)dev, dev_attr, prop_buf);
>> +   ret = power_supply_format_property((struct device *)dev, true, dev_attr, prop_buf);
>>     if (ret == -ENODEV || ret == -ENODATA) {
>>         /*
>>          * When a battery is absent, we expect -ENODEV. Don't abort;
>>