Date:   Thu, 7 Sep 2017 15:13:53 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Johannes Stezenbach <js@...21.net>,
        Hans de Goede <hdegoede@...hat.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        platform-driver-x86@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/3] mfd: Add support for Cherry Trail Dollar Cove TI
 PMIC

On Thu, 07 Sep 2017, Takashi Iwai wrote:

> On Thu, 07 Sep 2017 15:00:01 +0200,
> Lee Jones wrote:
> > 
> > > > > > > > > > > > > This patch adds the MFD driver for Dollar Cove (TI version) PMIC with
> > > > > > > > > > > > > ACPI INT33F5 that is found on some Intel Cherry Trail devices.
> > > > > > > > > > > > > The driver is based on the original work by Intel, found at:
> > > > > > > > > > > > >   https://github.com/01org/ProductionKernelQuilts
> > > > > > > > > > > > > 
> > > > > > > > > > > > > This is a minimal version for adding the basic resources.  Currently,
> > > > > > > > > > > > > only ACPI PMIC opregion and the external power-button are used.
> > > > > > > > > > > > > 
> > > > > > > > > > > > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=193891
> > > > > > > > > > > > > Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > > > > > > > > > > > Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
> > > > > > > > > > > > > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> > > > > > > > > > > > > ---
> > > > > > > > > > > > > v4->v5:
> > > > > > > > > > > > > * Minor coding-style fixes suggested by Lee
> > > > > > > > > > > > > * Put GPL text
> > > > > > > > > > > > > v3->v4:
> > > > > > > > > > > > > * no change for this patch
> > > > > > > > > > > > > v2->v3:
> > > > > > > > > > > > > * Rename dc_ti with chtdc_ti in all places
> > > > > > > > > > > > > * Driver/kconfig renames accordingly
> > > > > > > > > > > > > * Added acks by Andy and Mika
> > > > > > > > > > > > > v1->v2:
> > > > > > > > > > > > > * Minor cleanups as suggested by Andy
> > > > > > > > > > > > > 
> > > > > > > > > > > > >  drivers/mfd/Kconfig                   |  13 +++
> > > > > > > > > > > > >  drivers/mfd/Makefile                  |   1 +
> > > > > > > > > > > > >  drivers/mfd/intel_soc_pmic_chtdc_ti.c | 184 ++++++++++++++++++++++++++++++++++
> > > > > > > > > > > > >  3 files changed, 198 insertions(+)
> > > > > > > > > > > > >  create mode 100644 drivers/mfd/intel_soc_pmic_chtdc_ti.c
> > > > > > > > > > > > 
> > > > > > > > > > > > For my own reference:
> > > > > > > > > > > >   Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> > > > > > > > > > > 
> > > > > > > > > > > Thanks!
> > > > > > > > > > > 
> > > > > > > > > > > Now the question is how to deal with these.  It's no critical things,
> > > > > > > > > > > so I'm OK to postpone for 4.15.  OTOH, it's really a new
> > > > > > > > > > > device-specific stuff, thus it can't break anything else, and it'd be
> > > > > > > > > > > fairly safe to add it for 4.14 although it's at a bit late stage.
> > > > > > > > > > 
> > > > > > > > > > Yes, you are over 2 weeks late for v4.14.  It will have to be v4.15.
> > > > > > > > > 
> > > > > > > > > OK, I'll ring your bells again once when 4.15 development is opened.
> > > > > > > > 
> > > > > > > > Please don't.  Just collect all the Acks you have received and sent
> > > > > > > > out the set again changing [PATCH] for [RESEND].  Only if there
> > > > > > > > haven't been any code changes of course. 
> > > > > > >   
> > > > > > > You seem to have applied the patches in some branch, but still do I
> > > > > > > need to resend the whole patches?
> > > > > > 
> > > > > > That's up to the Platform Maintainers.
> > > > > > 
> > > > > > Since the MFD and ACPI are applied, you do not need to resend those.
> > > > > > 
> > > > > > > BTW, was patch 2/3 applied?  I miss your notification mail.
> > > > > > 
> > > > > > Patch 2 needs to be applied into the Platform tree.
> > > > > > 
> > > > > > Since there are no deps between the patches, they should be applied
> > > > > > into their own trees (as previously discussed).  I only applied the
> > > > > > ACPI patch because Rafael asked me nicely.  Normally this should have
> > > > > > gone in separately too.
> > > > > 
> > > > > Andy already expressed his preference about the patch going through
> > > > > MFD tree in the v5 thread.  Below is the excerpt.
> > > > 
> > > > If Andy is happy for me to apply the patch without an immutable
> > > > branch, then I'll take it.  But as I've already said, this it
> > > > non-optimal.
> > > > 
> > > > There is no reason why it can't be taken in via the Platform tree.
> > > > Nothing depends on it and it depends on nothing, since it is new
> > > > code.
> > > 
> > > That approach is also far from optimal, too, as Rafael and I
> > > explained.
> > 
> > That's just my point.  This approach is optimal.
> > 
> > The alternative is that I (or someone else) jumps through the required
> > hoops to create an immutable branch.  As a one off, it's not actually
> > that big of a deal.  However, if I do it for you, I have to do it for
> > every submitter, else it's not fair to them.
> 
> Lee, that's an overreaction.  No one would think that I'm special even
> if you would do that :)

I'm not saying you'd be special.  I'm saying if I do it for one, I
have to do it for others.

> I can create such a branch by myself, and send you pull requests, if

That is also an acceptable solution.

> it's a preferred way.  That's no problem.  It'd be much less time than
> discussing in a too lengthy thread, honestly speaking.  But maybe the
> problem isn't that...

The problem isn't time in the first instance.  It's the attempt to
avoid setting a precedence and for this to become the norm. 

> > MFD patch-sets inherently cross subsystem boundaries, which means I
> > would end up taking many more patches than I do already.  Subsequently
> > the per-cycle MFD pull-request exponentially grows in size, as does my
> > work load.
> 
> Yeah, I understand that.  OTOH, I don't understand the reason to
> refuse the IB as much possible -- there are several ways to manage
> that more easily.
> 
> For example, you can keep a persistent branch that can be branched off
> at any time for a new IB, while keeping another branch for regular,
> rather unstable patch applications.  For linux-next, you can provide
> the temporary merged branch, too.  It's a way some trees deploy.

Yes, I am aware that some repos split themselves up into immutable
branches, which can be independently pulled from.  They clearly have
more spare time than I do.

These branches are usually only split up by topic within their own
subject area/subsystem.  They tend not to be full of cross-sub system
patch-sets.

> > This is the way we've been working for years, and it works really
> > well.  I'm not about to change something which isn't broken, just to
> > avoid the really tiny corner-case you described before.
> 
> I'd disagree about it being a tiny corner-case.  It's fundamental to
> provide a solid code basis which user can test / development on.  If
> we do release kernels more frequently, it shouldn't be a problem.
> (e.g. for a fix between RC's, it's fine to merge through individual
> trees.)  But if the merge will be done first after 3 months, no one
> can guarantee what would happen in these 3 months.  That's why we need 
> the solid merge point to begin with.  It allows a way to debug for
> potential breakage after that point.

I agree.  Which is exactly what the current release model provides:

All patches get dumped into a pile and tagged (-rc1), then developers
get ~8 weeks to test their work and spot issues created by the merge
and have a chance to fix any problems found prior to final release.
It is this final release which forms the solid code base which you
speak of.

I haven't seen any issues that would warrant the over-the-top
cautionary steps which you suggest, where IMHO the maintenance burden
far outweighs the potential benefit.

Right, this really is enough now.

/out

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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