Re: [RFC] EC registers - Adding sysfs interface?

[Thomas Renninger <trenn@suse.de>]

On Thu, 2007-12-06 at 21:52 -0500, Len Brown wrote:
> On Wednesday 28 November 2007 11:28, Thomas Renninger wrote:
> > On Tue, 2007-11-13 at 19:03 +0000, Carlos Corbacho wrote:
> > > Alexey,
> > > 
> > > > How about character /dev/ec0?
> > > 
> > > Yes, that would be fine.
> > > 
> > > On Tuesday 13 November 2007 18:54:51 Alexey Starikovskiy wrote:
> > > > What is the benefit of having acer_acpi in userspace, rather than one more
> > > > *-laptop in /devices/misc?
> > > 
> > > A debate of "would it be easier for me to maintain an in kernel driver (if/ 
> > > when I can get it upstream) or a userspace application". At the moment, the 
> > > idea of a full blown userspace application is just something I'm toying with 
> > > in my head whilst working on WMI userspace.
> > 
> > I very much like the idea of a general EC debug/devel interface to
> > userspace.
> > It should be a separate CONFIG, marked "DEBUG", "EXPERIMENTAL" or
> > whatever and be per default off.
> > It is stupid that everybody who wants to debug a bit on EC registers
> > needs to duplicate the IBM EC implementation, this should IMO be moved
> > where it belongs to:
> > drivers/acpi/ec.c
> > 
> > The question is whether Len will accept/like it, Len?
> 
> 
> It is crazy to poke ioports from user-space when ec.c thinks it owns them.
> So if you're going to do so, it would certainly be an improvement
> to go through the driver rather than around it.
> 
> What other users of this interface would there be other than
> a user-space version of acer_acpi?
> If a user-space driver
> were using the I/F, then we couldn't make it a DEBUG-only feature,
> it would have to be enabled all the time.

I see the "danger" of applications misusing this as an interface and
implementing workarounds for unsupported ACPI parts and (this is the
real problem) stop working on the real problems or a proper
implementation.

Especially because this option should be compiled in e.g. OpenSUSE
versions, for better remote debugging (comparing EC register values with
DSDT Embedded Controller variable implementations on a related problem
could help a lot, without the need of digging in the dark for weeks...).

>From your comments above, I read out that you tend to accept such an
interface as suggested by Alexey?
Making it read-only by default, would mainly help debugging purposes and
should avoid any workaround implementations.

   Thomas