Hi Sourabh, On Fri, Apr 23, 2021 at 08:03:08AM -0700, Sourabh Banerjee wrote: > Hi All, > I need your suggestion on how to reconcile if the linux-libc-headers and > kernel versions are different? > For this discussion let's consider we are using the LTS branch YP-3.1 > (Dunfell). > With Dunfell let's consider following 3 cases: > > 1) Machine is supported on 5.4 kernel > *Kernel Recipe:* linux-yocto_5.4.bb > *libc-headers:* > meta/recipes-kernel/linux-libc-headers/linux-libc-headers_5.4.bb > There is no conflict in this case as libc-headers and linux-yocto are on same > version. > > 2) Machine is supported on a higher kernel (let's say 5.10) > *Kernel Recipe:* Let's assume provided by a BSP layer, linux_5.10.bb > *libc-headers:* > meta/recipes-kernel/linux-libc-headers/linux-libc-headers_5.4.bb > The kernel version is higher in this case. But, should be okay as 5.10 UAPI > is backward compatible and supports linux-libc-headers_5.4 completely. > > 3) Machine is supported on a lower kernel (let's say 4.19) > Kernel Recipe: Let's assume provided by a BSP layer, linux_4.19.bb > libc-headers: meta/recipes-kernel/linux-libc-headers/linux-libc-headers_5.4.bb > The kernel version is lower in this case. I suppose, this may lead to some > runtime issues? As the kernel built from 4.19 will not be able to support 5.4 > UAPI fully. > What's the recommendation here? Should the BSP provider port > linux-libc-header_4.19.bb in BSP layer and set > PREFERRED_VERSION_linux-libc-headers = "4.19%" >
The issue is that linux-libc-headers is not machine-specific, only distro-specific, so you'd need this PREFERRED_VERSION_linux-libc-headers specified in a distro (or local.conf for that matter, but... NO, please NO :) ). You could also technically provide your own linux-libc-headers in a layer of a higher priority and then PREFERRED_VERSION_linux-libc-headers won't matter as the highest prio layer's recipe will take precedence. But that is IMO bad practice as it means your distro has a different linux-libc-headers depending on whether a layer is included or not. I don't have a solution personally, just wanted to share why the last suggestion does not seem correct to me. Cheers, Quentin
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