Hi all,

It seems we don't have a consensus about what error code the device driver
should return in case a given driver API is not implemented. If we take a
look at suspend() and resume() functions, which are not implemented by some
device drivers, we can find three different return codes:
- DEV_OK: used in i2c_dw.c, i2c_atmel_sam3.c and gpio_sch.c
- DEV_INVALID_OP: used in pwm_dw.c, gpio_mmio.c and gpio_atmel_sam3.c
- DEV_NO_SUPPORT: used in i2c_qmsi.c and spi_qmsi.c

For these situations, a new error code (DEV_NOT_IMPLEMENTED) seems to be
applicable. If a new error code is not desired, we should agree on one
and use it in all device drivers.

Regards,

Andre