Re: [linux-usb-devel] [RFC PATCH] debugfs - yet another in-kernel file system

[Greg KH <greg@kroah.com>]

On Fri, Dec 10, 2004 at 05:29:01PM -0800, David Brownell wrote:
> On Thursday 09 December 2004 4:50 pm, Greg KH wrote:
> > What if there was a in-kernel filesystem that was explicitly just for
> > putting debugging stuff? ?Some place other than proc and sysfs, and that
> > was easier than both of them to use. ?Yet it needed to also be able to
> > handle complex stuff like seq file and raw file_ops if needed.
> 
> The problem with sysfs here is:  no seq_file support.
> Otherwise it solves the basic "where to put the debug
> files associated with "device X" or "driver Y" problems
> in a good non-confusing way:  there are directories
> already set up for devices and for drivers.

Yes, but that's a design decision for sysfs.  no seq_file support is a
feature, not a shortcoming :)

> The problem with procfs here is that it doesn't have
> such a naming solution:  there's no automatic mapping
> betwen a /proc/driver/...file and its device, or vice
> versa.  That issue is shared with debugfs.

Agreed.

> Couldn't debugfs just be a thin shim on top of sysfs,
> adding seq_file support?  Or on top of procfs, adding
> device/driver naming domains, and maybe file-per-value
> read/write support for drivers that want them?

Ick.

> What I'd really want out of a debug file API is to resolve
> the naming issues, work with seq_file, and "softly and
> silently vanish away".  I think this patch has the last
> two, but not the first one!

I considered adding a kobject as a paramater to the debugfs interface.
The file created would be equal to the path that the kobject has.  Would
that work for you?

thanks,

greg k-h