On 02/12/2016 05:52 AM, Andre Guedes wrote:

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

We definitely need to have one answer all drivers agree on.

I had an RFC where the suspend/resume functions move to the device
level and out of the device type specific APIs. This allows the PM
app/subsystem/entity to call the PM functions without needing to
know the type of the device.

I think I had agreement on the RFC but it fell by the wayside as we
were creeping up on the release date. I will get it rebased and
published again. Once we get agreement we can appoint all the
stuckies to update the drivers accordingly.

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.

In the new model the functions would be required to be implemented, the
RFC included a null implementation for drivers to use if they had no
work to do during suspend/resume. Still a topic for discussion but the
null functions can just return success meaning I have done everything
I need to or can do :-).

Regards,

Andre