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

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: d3ab61ecbab2 ("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>

0 files changed, 0 insertions, 0 deletions