power_supply: Add support for writeable properties

This patch adds support for writeable power supply properties and
exposes them as writeable to sysfs.

A power supply implementation must implement two new function calls in
order to use that feature:

  int set_property(struct power_supply *psy,
                   enum power_supply_property psp,
                   const union power_supply_propval *val);

  int property_is_writeable(struct power_supply *psy,
                            enum power_supply_property psp);

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Alexey Starikovskiy <astarikovskiy@suse.de>
Cc: Len Brown <len.brown@intel.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Matt Reimer <mreimer@vpop.net>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

2 files changed, 40 insertions, 3 deletions

diff --git a/drivers/power/power_supply_sysfs.c b/drivers/power/power_supply_sysfs.c
index 7d7593cad7d9..6a86cdfd79fa 100644
--- a/drivers/power/power_supply_sysfs.c
+++ b/drivers/power/power_supply_sysfs.c
@@ -33,7 +33,7 @@
 {                                                                       \
         .attr = { .name = #_name },                                     \
         .show = power_supply_show_property,                             \
-        .store = NULL,                                                  \
+        .store = power_supply_store_property,                           \
 }
 
 static struct device_attribute power_supply_attrs[];
@@ -99,6 +99,29 @@ static ssize_t power_supply_show_property(struct device *dev,
         return sprintf(buf, "%d\n", value.intval);
 }
 
+static ssize_t power_supply_store_property(struct device *dev,
+                                           struct device_attribute *attr,
+                                           const char *buf, size_t count) {
+        ssize_t ret;
+        struct power_supply *psy = dev_get_drvdata(dev);
+        const ptrdiff_t off = attr - power_supply_attrs;
+        union power_supply_propval value;
+        long long_val;
+
+        /* TODO: support other types than int */
+        ret = strict_strtol(buf, 10, &long_val);
+        if (ret < 0)
+                return ret;
+
+        value.intval = long_val;
+
+        ret = psy->set_property(psy, off, &value);
+        if (ret < 0)
+                return ret;
+
+        return count;
+}
+
 /* Must be in the same order as POWER_SUPPLY_PROP_* */
 static struct device_attribute power_supply_attrs[] = {
         /* Properties of type `int' */
@@ -159,8 +182,17 @@ static mode_t power_supply_attr_is_visible(struct kobject *kobj,
         int i;
 
         for (i = 0; i < psy->num_properties; i++) {
-                if (psy->properties[i] == attrno)
-                        return 0444;
+                int property = psy->properties[i];
+
+                if (property == attrno) {
+                        mode_t mode = S_IRUSR | S_IRGRP | S_IROTH;
+
+                        if (psy->property_is_writeable &&
+                            psy->property_is_writeable(psy, property) > 0)
+                                mode |= S_IWUSR;
+
+                        return mode;
+                }
         }
 
         return 0;
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index c5f73a3ab3ab..30083a896f36 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -145,6 +145,11 @@ struct power_supply {
         int (*get_property)(struct power_supply *psy,
                             enum power_supply_property psp,
                             union power_supply_propval *val);
+        int (*set_property)(struct power_supply *psy,
+                            enum power_supply_property psp,
+                            const union power_supply_propval *val);
+        int (*property_is_writeable)(struct power_supply *psy,
+                                     enum power_supply_property psp);
         void (*external_power_changed)(struct power_supply *psy);
         void (*set_charged)(struct power_supply *psy);