Re: [PATCH v4] platform/x86: ideapad-laptop: Add sysfs interface for touchpad state

From: Darren Hart
Date: Mon May 01 2017 - 15:16:40 EST

On Mon, May 01, 2017 at 11:57:27PM +0530, Ritesh Raj Sarraf wrote:
> On Mon, 2017-05-01 at 09:05 -0700, Darren Hart wrote:
> > > sysfs ABI for drivers that provide input interface is quite strong for
> > > my opinion. It means I'm not totally objecting, but I would accept it
> > > if and only if there is nothing else could be done.
> >
> > Agreed, we've recently wanted to remove certain sysfs attributes from another
> > driver as they were obsolete and better implemented in other ways, but once
> > they
> > are there, are hands are tied.
> >
> > That said, we will support getting these systems functional. From what I see
> > in
> > the patch you are implementing a polling sysfs interface. Have you verified
> > that
> > there is no event we can capture and send the SW_TABLET_MODE along to the
> > input
> > system?
> I believe it does generate an event (at least on my Yoga 2 13 variant). IIRC,
> when I talked to Andy initially about the driver's limitation, we did do an
> exercise [1] to determine if an event was generated.
> Cooking this patch (sysfs interface) was much quicker and easy. I looked at the
> other example drivers, that do SW_TABLET_MODE, but left it there. I don't think
> I have all the necessary information to get that done for the ideapad driver.
> [1]

Thanks. We really want to avoid user-space having to write platform specific
sysfs attribute access to determine system state for common things like "should
I show the on screen keyboard?". That doesn't scale and will result in a very
sparse support matrix in general.

Something I am not particularly well versed in is the issue with hotkeys,
xinput, and only working in Xorg rather than wayland. Where in the stack is this
limitation created? I assume it is above the kernel - no reason Wayland can't
read SW_TABLET_MODE from the input subsystem correct?

I believe I have a couple systems which will replicate this issue so I'll try to
spend some time with them to see what else might be done.

Darren Hart
VMware Open Source Technology Center