Re: [PATCH] drm/i2c: tda998x: don't register the connector

[Brian Starkey]

On Thu, Sep 22, 2016 at 01:28:37PM +0200, Daniel Vetter wrote:
> On Thu, Sep 22, 2016 at 1:22 PM, Sean Paul <seanpaul@xxxxxxxxxxxx> wrote:
> > On Thu, Sep 22, 2016 at 3:51 AM, Russell King - ARM Linux
> > <linux@xxxxxxxxxxxxxxx> wrote:
> > > On Thu, Sep 22, 2016 at 11:39:18AM +0100, Brian Starkey wrote:
> > > > Actually, could you please hold off picking this up? We need to make
> > > > changes in mali-dp and hdlcd or this will mess up their registration.
> > > > I will send those patches later today, but better if this all goes in
> > > > together (whenever that ends up being).
> > >
> > > Sorry, but I'm annoyed with this - the impression being given was that
> > > I was holding up this patch by not testing it on Armada, and I brought
> > > up the issue about registration at the beginning of this.

Sorry, this was poor on my part. There's no-one who will care about
Mali-DP, but I had forgotten that this would also break HDLCD.

> > > Now we're _just_ finding out that there are drivers where removing the
> > > connector registration in tda998x causes them to break?  It's a bit
> > > late to be checking your own drivers when you've been chasing me...

It's not like I didn't check our drivers, more that I should have sent
a full series for all three drivers together in the first place.

However, without patching all three drivers in the same commit, there
would always be some breakage. HDLCD and Mali-DP call
drm_dev_register() before binding the components - this was needed to
work with tda998x, which needed the device to be already registered
before its bind callback runs.

It's more proper to call drm_dev_register() as the very last thing
(i.e. after component_bind_all()) to avoid races with userspace - but
I couldn't do that without this change in tda998x first.

> > > Sorry, but it sounds like we're not ready to make this change - and as
> > > it's the very last day that changes will appear in linux-next prior to
> > > the merge window (assuming Linus releases 4.8 on Sunday), I'd suggest
> > > holding off until after the merge window is over, so we can get some
> > > testing with these other two drivers with this change in place.
> >
> > sigh. I just pushed my queue to drm-misc, which included this patch.
> > Sounds like I should revert?
>
> I thought I looked at the entire situation and since we register
> (since recently) all connectors in drm_dev_register() there shouldn't
> be an issue for any other driver. Imo no need to revert anything here
> - until someone complains with a bug report and proves me wrong ;-)

Yeah... this does indeed break HDLCD and Mali-DP. They register the
device, then bind tda998x which init's its connector. The connector
ends up in the connector_list, but not the idr.

I don't know how widely HDLCD on Juno is used (for anyone to notice).

-Brian

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch