Re: [RFC:PATCH dtc-1.3.0] dtc: Add --strip-disabled option to dtc.

[David Gibson <dwg-8fk3Idey6ehBDgjK7y7TUQ@public.gmane.org>]

On Mon, Aug 20, 2012 at 09:36:22AM +0100, Srinivas KANDAGATLA wrote:
> On 17/08/12 16:36, Timur Tabi wrote:
> > Srinivas KANDAGATLA wrote:
> >> If you know in advance that device on that SOC is broken, then I guess
> >> "Fail"/"Failed" can be used in status property.
> >>
> >> One user of this flag in kernel device trees is
> >> ./arch/powerpc/boot/dts/mpc8313erdb.dts
> > 	/* Remove this (or change to "okay") if you have
> > 	 * a REVA3 or later board, if you apply one of the
> > 	 * workarounds listed in section 8.5 of the board
> > 	 * manual, or if you are adapting this device tree
> > 	 * to a different board.
> > 	 */
> > 	status = "fail";
> >
> > I'm not sure this is the right way to do it. 
> I agree, the way fail status is used is pretty much redundant to what
> "disabled" is used for.
> I think the device trees files should have status as "okay" or "ok" or
> "disabled" or skip status property totally.
> 
> >  Normally, the boot loader
> > should be able to detect the board revision, and it should dynamically set
> > the 'status'.  We have other devices that fail if a work-around is not
> > applied, and we don't use this approach.
> >
> > But assuming that this really is the best approach, then it would make
> > sense for --strip-disabled to leave this node in the dtb, because
> > otherwise there would be no way to re-enable it.
> --strip-disabled should still get rid for nodes marked as failed
> as-well, because fail means something serious and un-recoverable.
> 
> I think bootloader should not even consider nodes with status as
> fail, as the device is unlikely to become operational without
> repair.

I do worry about the usability implications of that - if a device that
was previously working stops working and is marked as "failed" it's
fairly easy for the user/admin to see what's going on.  If the device
simply vanishes completely that would be rather more mysterious.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson