Re: [PATCH 2/4] drm/i2c: tda998x: Remove obsolete drm_connector_register() call

[Russell King - ARM Linux <linux@armlinux.org.uk>]

On Wed, Oct 19, 2016 at 10:46:48AM +0100, Brian Starkey wrote:
> Hi Jyri,
> 
> I believe this will break mali-dp and hdlcd, unless something changed
> while I wasn't looking. Please see this previous thread where I did
> the same thing and then had to have it reverted: [1]
> 
> Before removing this, we need to refactor (at least) mali-dp and hdlcd
> to move drm_dev_register() to the end of their ->bind() callback.
> 
> That could be done without moving drm_dev_unregister() to the start
> of ->unbind() if you really want to nuke the drm_connector_register()
> call, but to maintain symmetry (and introduce correctness) I was
> putting it off until I had a chance to remove drm_vblank_cleanup()
> from drm_dev_unregister() (because [2]).

So what is the status of this - when is it going to happen?  Without
this happening, I can't de-midlayer armada-drm, and I can't apply
these TDA998x patches.

As armada-drm stands at the moment, it can cope with the TDA998x
driver having the drm_connector_register(), or with it eliminated.
When armada-drm is de-midlayered without changing TDA998x, the
drm_connector_register() call in TDA998x produces a warning:

WARNING: CPU: 0 PID: 13 at lib/kobject.c:244 kobject_add_internal+0xfc/0x2d8
kobject_add_internal failed for card0-HDMI-A-1 (error: -2 parent: card0)

I suspect that you will end up with the same problem when you move
the drm_dev_register() call after component_bind_all() - and I think
the answer is... you shouldn't have de-midlayered until TDA998x had
been updated to cope with de-midlayering, iow having had the
drm_connector_register() call removed.

Given that, I don't think we can avoid breaking mali-dp and hdlcd,
except by combining the change into a single patch, changing all three
drivers simultaneously (and any other driver which uses TDA998x which
has also been de-midlayered.)

So, what I would like to see is a single patch against Linus' 4.8.0
commit fixing mali-dp, hdlcd and any other driver, together with
removing drm_connector_register() from TDA998x.  This is so the patch
can be shared between all interested parties without forcing everyone
to 4.9-rc1.  Looking at the diff between 4.8 and 4.9-rc1 for
drivers/gpu/drm/arm, that shouldn't result in any merge conflicts -
and if you want to follow on from that with 4.9-rc1 development, you
can always merge 4.9-rc1 on top of that commit.

I'm happy to take such a patch and publish it via my git tree as part
of the TDA998x development if that helps - but either way we need it
shared between all parties.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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