[PATCH 0/2] hwmon: Add PEC attribute support to hardware monitoring core

[Guenter Roeck <linux@roeck-us.net>]

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.

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