Re: [PATCH v2] HID: i2c-hid: wait for i2c touchpad deep-sleep to power-up transition

[Johan Hovold]

On Tue, Apr 09, 2024 at 12:53:43PM +0200, Łukasz Majczak wrote:

> > Can you please explain why this would not a problem for all future
> > transactions as well?

> The problem is that the probe function calling i2c_smbus_read_byte()
> is not aware that
> uC on the other end is in a deep sleep state so the first read will
> fail and so the whole probe.
> 
> In a normal scenario, when a user touches the touchpad (when it is in
> a deep sleep), the touch will first wake up the uC and
> then generate an interrupt to AP, so in this case the touchpad is
> fully awake and operational.

Sure, but what about other transactions that are initiated by the host
(e.g. SET_POWER)?

Perhaps this hack at probe is enough for your use case, but is an
incomplete hack and at a minimum you'd need to add a comment explaining
why it is there.

Johan