mlxsw: core_thermal: Fix -Wformat-truncation warning

The name of a thermal zone device cannot be longer than 19 characters
('THERMAL_NAME_LENGTH - 1'). The format string 'mlxsw-lc%d-module%d' can
exceed this limitation if the maximum number of line cards cannot be
represented using a single digit and the maximum number of transceiver
modules cannot be represented using two digits.

This is not the case with current systems nor future ones. Therefore,
increase the size of the result buffer beyond 'THERMAL_NAME_LENGTH' and
suppress the following build warning [1].

If this limitation is ever exceeded, we will know about it since the
thermal core validates the thermal device's name during registration.

[1]
drivers/net/ethernet/mellanox/mlxsw/core_thermal.c: In function ‘mlxsw_thermal_modules_init.part.0’:
drivers/net/ethernet/mellanox/mlxsw/core_thermal.c:418:70: error: ‘%d’ directive output may be truncated writing between 1 and 3 bytes into a region of size between 2 and 4 [-Werror=format-truncation=]
  418 |                 snprintf(tz_name, sizeof(tz_name), "mlxsw-lc%d-module%d",
      |                                                                      ^~
In function ‘mlxsw_thermal_module_tz_init’,
    inlined from ‘mlxsw_thermal_module_init’ at drivers/net/ethernet/mellanox/mlxsw/core_thermal.c:465:9,
    inlined from ‘mlxsw_thermal_modules_init.part.0’ at drivers/net/ethernet/mellanox/mlxsw/core_thermal.c:500:9:
drivers/net/ethernet/mellanox/mlxsw/core_thermal.c:418:52: note: directive argument in the range [1, 256]
  418 |                 snprintf(tz_name, sizeof(tz_name), "mlxsw-lc%d-module%d",
      |                                                    ^~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/mellanox/mlxsw/core_thermal.c:418:17: note: ‘snprintf’ output between 18 and 22 bytes into a destination of size 20
  418 |                 snprintf(tz_name, sizeof(tz_name), "mlxsw-lc%d-module%d",
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  419 |                          module_tz->slot_index, module_tz->module + 1);
      |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ido Schimmel <[email protected]>
Reviewed-by: Vadim Pasternak <[email protected]>
Signed-off-by: Petr Machata <[email protected]>
Reviewed-by: Wojciech Drewek <[email protected]>
Link: https://patch.msgid.link/583a70c6dbe75e6bf0c2c58abbb3470a860d2dc3.1722345311.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <[email protected]>

Author: idosch

drivers/net/ethernet/mellanox/mlxsw/core_thermal.c

@@ -411,7 +411,7 @@ static const struct thermal_cooling_device_ops mlxsw_cooling_ops = {
 static int
 mlxsw_thermal_module_tz_init(struct mlxsw_thermal_module *module_tz)
 {
-	char tz_name[THERMAL_NAME_LENGTH];
+	char tz_name[40];
 	int err;
 
 	if (module_tz->slot_index)