Hi Krzysztof, On Mon, Sep 27, 2021 at 10:08 AM Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx> wrote: > On 25/09/2021 04:17, Saravana Kannan wrote: > > On Tue, Sep 21, 2021 at 1:25 AM Krzysztof Kozlowski > > <krzysztof.kozlowski@xxxxxxxxxxxxx> wrote: > >> On 21/09/2021 10:11, Lee Jones wrote: > >>> On Tue, 21 Sep 2021, Krzysztof Kozlowski wrote: > >>>> On 20/09/2021 21:03, Will McVicker wrote: > >>>>> This patch series tries to address the issue of ARCH_EXYNOS force selecting > >>>>> a handful of drivers without allowing the vendor to override any of the > >>>>> default configs. This takes away from the flexibilty of compiling a generic > >>>>> kernel with exynos kernel modules. For example, it doesn't allow vendors to > >>>>> modularize these drivers out of the core kernel in order to share a generic > >>>>> kernel image across multiple devices that require device-specific kernel > >>>>> modules. > >>>> > >>>> You do not address the issue in these patches. The problem you describe > >>>> is that drivers are not modules and you are not changing them into modules. > >>> > >>> The wording is unfortunate. The reason for this change doesn't have > >>> much to do with kernel modules. > >>> > >>> Let's go back in time 18 months or so when Greg KH submitted this [0] > >>> patch, which you Acked. Greg was trying to solve the problem of not > >>> having to enable ARCH_EXYNOS on kernels which are designed to be > >>> platform agnostic (sometimes called Generic Kernels). For some reason > >>> SERIAL_SAMSUNG is the only symbol with these dependencies, so the > >>> solution seemed simple and straight forward at the time. > >>> > >>> However, For sound reasons Geert NACKed the patch. > >>> > >>> Quoting from [1] he says: > >>> > >>> "A generic kernel will include Samsung SoC support, hence > >>> PLAT_SAMSUNG or ARCH_EXYNOS will be enabled." > >> > >> Yes, it's correct reasoning. There is also one more use-case - > >> non-upstreamed (out of tree) platform which wants to use Exynos-specific > >> drivers. Something like was happening with Apple M1 except that it got > >> upstreamed and we do not care much about out-of-tree. > >> > >>> However, since the entry for ARCH_EXYNOS *insists* on building-in a > >>> bunch of other symbols (via 'select') which will be unused in most > >>> cases, this is not a currently acceptable approach for many Generic > >>> Kernels due to size constraints. > >> > >> In the mainline kernel there is no such use case. If you want to have > >> Exynos-whatever-driver (e.g. SERIAL_SAMSUNG or S3C RTC), you should > >> select ARCH_EXYNOS because otherwise it does not make any sense. Zero > >> sense. Such kernel won't work. > >> > >> It makes sense only if there is some other work, hidden here, where > >> someone might want to have SERIAL_SAMSUNG or S3C RTC without > >> ARCH_EXYNOS. Although GKI is not that work because GKI kernel will > >> select ARCH_EXYNOS. It must select ARCH_EXYNOS if it wants to support > >> Exynos platforms. > >> > >> Therefore I expect first to bring this "some other work, hidden here" to > >> broader audience, so we can review its use case. > >> > >>> What this patch does is migrates those symbols from being 'select'ed > >>> (always built-in with no recourse) to 'default y'. Where the former > >>> cannot be over-ridden, but the latter can be via a vendor's > >>> defconfig/fragment. > >> > >> It cannot be overridden by vendor fragment because options are not > >> visible. You cannot change them. > >> > >> The patch does nothing in this regard (making them selectable/possible > >> to disable), which is why I complained. > >> > >>> I doubt many (any?) of these symbols can be converted to kernel > >>> modules anyway, as they are required very early on in the boot > >>> sequence. > >> > >> True, some could, some not. Also some platforms are set up via > >> bootloader, so actually could "survive" till module is loaded from some > >> initrd. > > > > I was trying to chime in, but the discussion got spread out across all > > the patches. Since the cover letter seems to have everyone, I thought > > I'd reply here. Hope you don't mind. I'll try to respond/chime in on > > the various topics that were raised across the patches. > > > > Yes, the next patch series would To/Cc folks correctly. William simply > > forgot to use the --to-cover and --cc-cover options when using git > > send-email. > > > > I agree with you that it doesn't make sense to have ARCH_EXYNOS > > enabled but to have all the clock drivers exynos compiled out. Then > > one obviously can't boot an exynos platform using that kernel. > > If downstream kernel does not use any upstream platforms (e.g. > Exynos5433 or Exynos7) and has its own drivers for everything, then > downstream does not even need ARCH_EXYNOS. Just disable it. I guess that's how they got to "[PATCH 1/2] tty: serial: samsung_tty: build it for any platform"... https://lore.kernel.org/lkml/20200220102628.3371996-1-gregkh@xxxxxxxxxxxxxxxxxxx/ Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
