Messages in this thread | | | Subject | Re: Dynamic overlay failure in 4.19 & 4.20 | From | Phil Elwell <> | Date | Tue, 4 Jun 2019 20:39:04 +0100 |
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Hi Frank,
On 04/06/2019 19:20, Frank Rowand wrote: > Hi Phil, > > On 6/4/19 5:15 AM, Phil Elwell wrote: >> Hi, >> >> In the downstream Raspberry Pi kernel we are using configfs to apply overlays at >> runtime, using a patchset from Pantelis that hasn't been accepted upstream yet. >> Apart from the occasional need to adapt to upstream changes, this has been working >> well for us. >> >> A Raspberry Pi user recently noticed that this mechanism was failing for an overlay in >> 4.19. Although the overlay appeared to be applied successfully, pinctrl was reporting >> that one of the two fragments contained an invalid phandle, and an examination of the >> live DT agreed - the target of the reference, which was in the other fragment, was >> missing the phandle property. >> >> 5.0 added two patches - [1] to stop blindly copying properties from the overlay fragments >> into the live tree, and [2] to explicitly copy across the name and phandle properties. >> These two commits should be treated as a pair; the former requires the properties that >> are legitimately defined by an overlay to be added via a changeset, but this mechanism >> deliberately skips the name and phandle; the latter addresses this shortcoming. However, >> [1] was back-ported to 4.19 and 4.20 but [2] wasn't, hence the problem. > > I have relied upon Greg's statement that he would handle the stable kernels, and that > the process of doing so would not impact (or would minimally impact) maintainers. If > I think something should go into stable, I will tag it as such, but otherwise I ignore > the stable branches. For overlay related code specifically, my base standard is that > overlay support is an under development, not yet ready for prime time feature and thus > I do not tag my overlay patches for stable. > > Your research and analysis above sound like there are on target (thanks for providing > the clear and detailed explanation!), so if you want the stable branches to work for > overlays (out of tree, as you mentioned) I would suggest you email Greg, asking that > the second patch be added to the stable branches. Since the two patches you pointed > out are put of a larger series, you might also want to check which of the other > patches in that series were included in stable or left out from stable. My suggestion > that you request Greg add the second patch continues to rely on the concept that > stable does not add to my workload, so I have not carefully analyzed whether adding > the patch actually is the correct and full fix, but instead am relying on your good > judgment that it is.
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Thank you - I'll email Greg directly as you suggest, with your answer as supporting evidence.
Phil
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