[Intel-gfx] [RFC 00/12] Support for sustained capturing of GuC firmware logs

[Johannes Berg]

On Thu, 2016-06-02 at 10:16 +0000, Daniel Vetter wrote:

> I still kinda like relayfs, except that it's not available in non-
> debug builds. But so are plenty of other really interesting files we
> have hidden in there.
> 
> sysfs isn't the solution, I already have a black eye from the sysfs
> maintainer for our error state.

Heh. I tend to agree though.

> No idea really where to put stuff. One option might be to have an
> official debug directory (like we have power already) in sysfs as the
> canonical place where drivers can dump stuff. We're not the only ones
> with too much data to get to userspace for debugging driver/hw
> issues, e.g. wireless firmware has pretty similar solutions.

We have two things in wireless:

 1) the devcoredump stuff, but that's a one-time event when something 
    bad happens and dumps a big blob into userspace, doesn't seem
    relevant here

 2) continuous logging, which uses a debugfs file (though it could be
    relayfs as well, doesn't really make a difference)

There could be something said for using tracing, but that's only
independent of debugfs since the tracefs introduction in kernel 4.1.

johannes