Re: [GIT PULL] commits for Linux 4.4

From: Nathan Chancellor <natechancellor@gmail.com>
To: Timur Tabi <timur@codeaurora.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Sasha Levin <Alexander.Levin@microsoft.com>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [GIT PULL] commits for Linux 4.4
Date: Fri, 27 Apr 2018 11:04:46 -0700	[thread overview]
Message-ID: <20180427180446.GA18615@flashbox> (raw)
In-Reply-To: <6cd50d5c-89ec-b484-d684-6ee316575d87@codeaurora.org>

On Fri, Apr 27, 2018 at 03:40:50AM -0500, Timur Tabi wrote:
> On 4/27/18 2:35 AM, Nathan Chancellor wrote:
> > > That's not good.  Have you reported this to the gpio developers and
> > > authors of that patch?
> > > 
> > I have not although I've gone ahead and CC'd them on this email.
> > 
> > > > I'm happy to carry the revert in my tree given it is probably a correct
> > > > change in mainline but I figured I would let you guys know so you can
> > > > make that decision.
> > > Ah, do you think this is a userspace issue with your device and not a
> > > kernel problem?  That implies that this patch isn't ok and should be
> > > reverted upstream.
> > > 
> > I don't think this is a userspace regression. My guess is certain
> > out of tree drivers expect a static base value, based on the wording
> > of the commit message. Unfortunately, his is all a little bit over
> > my head at the moment. I will try to study up on it tomorrow. I just
> > wanted to report the regression as soon as I uncovered it (I'd be
> > lying if I said I liked reporting bugs heh).
> 
> Apparently, user-space should no longer be depending on any base value.
> Instead, gpiolib should be used.  I'm guessing that the Pixel 2 XL does not
> use gpiolib, since gpiolib didn't exist until Linux 4.8.
> 
> So I think that this patch should be reverted in 4.4.
> 
> When the patch was submitted, I proposed an alternative that would preserve
> existing platforms but still support gpiolib and newer systems with multiple
> TLMMs:
> 
> 	https://lkml.org/lkml/2018/2/7/360
> 
> I thought it was a good compromise, but it was rejected.
> 
> -- 
> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
> Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
> Code Aurora Forum, a Linux Foundation Collaborative Project.

Thank you very much for the quick response and explanation. Makes
perfect. Glad we caught it before it even made it into an RC release.

Cheers!
Nathan