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power: supply: sbs-battery: Use a per-device serial number buffer

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sbs_get_battery_serial_number() formats the battery serial number into
sbs_serial[], a single file-scope buffer shared by every sbs-battery
instance, and points val->strval at it.

Nothing restricts this driver to one instance. It binds per I2C client,
and sbs-manager registers one muxed I2C channel per supported battery
specifically so that the smart battery driver can be bound to each of
them, so several sbs-battery instances on one system is a supported
configuration.

The power supply core reads strval after the driver's get_property()
callback has returned: power_supply_show_property() fills a local
union power_supply_propval, then formats it with sysfs_emit(). Two
concurrent POWER_SUPPLY_PROP_SERIAL_NUMBER reads on different batteries
therefore race for the shared buffer - battery B's sprintf() can land
between battery A filling the buffer and the core reading it, and
battery A then reports battery B's serial number.

Move the buffer into struct sbs_info so that each battery formats into
its own storage. It is deliberately not added to the chip->strings[]
array: those entries hold the cached constant strings that
sbs_invalidate_cached_props() clears on presence changes, whereas the
serial number is re-read from its word register on every access.

Fixes: d3ab61ecba ("bq20z75: Add support for more power supply properties")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Babanpreet Singh <bbnpreetsingh@gmail.com>
Link: https://patch.msgid.link/20260726072206.7-2-bbnpreetsingh@gmail.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
This commit is contained in:
Babanpreet Singh
2026-07-26 07:22:05 +00:00
committed by Sebastian Reichel
parent df55823b98
commit 6027892925
1 changed files with 4 additions and 3 deletions
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7
drivers/power/supply/sbs-battery.c
View File

@@ -217,6 +217,7 @@ struct sbs_info {
u32 flags;
int technology;
char strings[NR_STRING_BUFFERS][I2C_SMBUS_BLOCK_MAX + 1];
char serial[5];
};
static char *sbs_get_string_buf(struct sbs_info *chip,
@@ -821,18 +822,18 @@ static int sbs_get_battery_capacity(struct i2c_client *client,
return 0;
}
static char sbs_serial[5];
static int sbs_get_battery_serial_number(struct i2c_client *client,
union power_supply_propval *val)
{
struct sbs_info *chip = i2c_get_clientdata(client);
int ret;
ret = sbs_read_word_data(client, sbs_data[REG_SERIAL_NUMBER].addr);
if (ret < 0)
return ret;
sprintf(sbs_serial, "%04x", ret);
val->strval = sbs_serial;
sprintf(chip->serial, "%04x", ret);
val->strval = chip->serial;
return 0;
}