* Arnd Bergmann <arnd@xxxxxxxxxx> [210122 11:24]: > On Thu, Jan 21, 2021 at 8:57 PM Suman Anna <s-anna@xxxxxx> wrote: > > On 1/21/21 12:39 PM, Nishanth Menon wrote: > > > On 12:13-20210121, Suman Anna wrote: > > >> > > >> Hmm, this is kinda counter-intuitive. When I see a dts node, I am expecting the > > > > > > What is counter intutive about a -next branch be tested against > > > linux-next tree? > > > > The -next process is well understood. FWIW, you are not sending your PR against > > -next branch, but against primarily a -rc1 or -rc2 baseline. > > > > As a developer, when I am submitting patches, I am making sure that things are > > functional against the baseline you use. For example, when I split functionality > > into a driver portions and dts portions, I need to make sure both those > > individual pieces boot fine and do not cause regressions, even though for the > > final functionality, you need both. > > > > > > > > > Now, if you want to launch a product with my -next branch - go ahead, I > > > don't intent it for current kernel version - you are on your own. > > > > > > If there is a real risk of upstream next-breaking - speakup with an > > > real example - All I care about is keeping upstream functional and > > > useable. > > > > This is all moot when your own tree doesn't boot properly. In this case, you are > > adding MMC nodes, but yet for a boot test, you are saying use linux-next for the > > nodes that were added or you need additional driver patches (which is not how > > maintainer-level trees are verified). > > > > Arnd, > > Can you please guide us here as to what is expected in general, given that the > > pull-request from Nishanth goes through you, and if there is some pre-existing > > norms around this? > > There are two very different cases to consider, and I'm not sure which one > we have here: > > - When submitting any changes to a working platform, each patch on > a branch that gets merged needs to work incrementally, e.g. a device > tree change merged through the soc tree must never stop a platform > from booting without a patch that gets merged through another branch > in the same merge window, or vice versa. > As an extension of this, I would actually appreciate if we never do > incompatible binding changes at all. If a driver patch enables a new > binding for already supported hardware, a second patch changes > the dts file to use the new binding, and a third patch removes the > original binding, this could still be done without regressions over > multiple merge windows, but it breaks the assumption that a new > kernel can boot with an old dtb (or vice versa). This second one > is a softer requirement, and we can make exceptions for particularly > good reasons, but please explain those in the patch description and > discuss with upstream maintainers before submitting patches that do > this. > > - For a newly added hardware support, having a runtime dependency > on another branch is not a problem, we do that all the time: Adding > a device node for an existing board (or a new board) and the driver > code in another branch is not a regression because each branch > only has incremental changes that improve hardware support, and > it will work as soon as both are merged. > You raised the point about device bindings, which is best addressed > by having one commit that adds the (reviewed) binding document > first, and then have the driver branch and the dts branch based on > the same commit. > > I hope that clarifies the case you are interested in, let me know if I > missed something for the specific case at hand. Hmm and additionally few more mostly obvious things that have helped quite a bit: - Each commit in each topic branch should compile and boot so git bisect works - Each topic branch should be ideally based on -rc1 to leave out dependencies to other branches - Aiming for a working and usable -rc1 is worth the effort in case git bisect is needed for any top branches based on it :) Otherwise you'll be wasting the -rc cycle chasing regressions.. Regards, Tony
