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