Several hardware monitoring chips optionally support Packet Error Checking (PEC). For some chips, PEC support can be enabled simply by setting I2C_CLIENT_PEC in the i2c client data structure. Others require chip specific code to enable or disable PEC support. Introduce hwmon_chip_pec and HWMON_C_PEC to simplify adding configurable PEC support for hardware monitoring drivers. A driver can set HWMON_C_PEC in its chip information data to indicate PEC support. If a chip requires chip specific code to enable or disable PEC support, the driver only needs to implement support for the hwmon_chip_pec attribute to its write function. The hardware monitoring core does not depend on the I2C subsystem after this change. However, the I2C subsystem needs to be reachable. This requires a new HWMON dependency to ensure that HWMON can only be built as module if I2C is built as module. This should not make a practical difference. The first patch of the series introduces PEC support to the harwdare monitoring core. The second patch converts to lm90 driver to use the new infrastructure. Tested with ADM7421A using lm90 driver and Devantech USB-ISS. ---
