[OpenWrt-Devel] [PATCH] kernel: modules: fix kmod-regmap

[Jonas Gorski]

On 1 August 2018 at 22:44, Christian Lamparter <chunkeey at gmail.com> wrote:
> On Wednesday, August 1, 2018 3:21:00 PM CEST Jonas Gorski wrote:
>> On 30 July 2018 at 22:35, John Crispin <john at phrozen.org> wrote:
>> > On 30/07/18 22:33, Christian Lamparter wrote:
>> >>
>> >> This patch fixes the a compile issue that was triggered by
>> >> apm821xx/sata when kmod-regmap was selected.
>> >>
>> >> The CONFIG_REGMAP is declared in drivers/base/regmap/Kconfig
>> >> as type "bool" and not "tristate". Hence the symbol should
>> >> never be set to module, as this confuses the #if CONFIG_REGMAP
>> >> guards in include/linux/regmap.h:
>> >>
>> >> |.../drivers/regulator/core.c:4041: undefined reference to
>> >> `dev_get_regmap'
>> >> |.../drivers/regulator/core.c:4042: undefined reference to
>> >> `dev_get_regmap'
>> >> |.../drivers/regulator/core.c:4044: undefined reference to
>> >> `dev_get_regmap'
>> >> |.../drivers/regulator/helpers.o: In function
>> >> `regulator_is_enabled_regmap':
>> >> |.../drivers/regulator/helpers.c:36: undefined reference to `regmap_read'
>> >> |...
>> >
>> > i started a test build 2 minutes ago to figure this one out :-) thanks !
>>
>> This is actually the wrong fix and papers over an issue in one of our
>> local patches.
>>
>> We intentionally allow regmap to be built as a module, see
>>
>> https://github.com/openwrt/openwrt/blob/master/target/linux/generic/hack-4.14/259-regmap_dynamic.patch
>>
>> So there are likely some additional EXPORT_SYMBOL_GPL()s required instead.
>
> Thanks for FYI, I missed this patch completely.
>
> I found that the issue lies in the upstream regulator core code.
> It is using these regmap's functions. And the CONFIG_REGULATOR symbol that pulls
> in the core's code is sadly a bool menuconfig option... so CONFIG_REGMAP pretty
> much becomes a requirement/select for the REGULATOR.

This is one of the more trickier variants, it optionally supports
regmap thanks to the stubs provided if regmap is disabled - which
breaks if you compile regmap as a module. I expect this to happen more
in the future.

This is a bit tricky to solve. We can't just generally stub out the
regmap stuff unless compiled in, as a lot of regulators depend on it.
A proper fix is likely a bit more work (as usual).

>
> ---
> diff --git a/target/linux/generic/hack-4.14/259-regmap_dynamic.patch b/target/linux/generic/hack-4.14/259-regmap_dynamic.patch
> index 1c6e78df30..35803c3181 100644
> --- a/target/linux/generic/hack-4.14/259-regmap_dynamic.patch
> +++ b/target/linux/generic/hack-4.14/259-regmap_dynamic.patch
> @@ -9,8 +9,9 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
>   drivers/base/regmap/Kconfig  | 15 ++++++++++-----
>   drivers/base/regmap/Makefile | 12 ++++++++----
>   drivers/base/regmap/regmap.c |  3 +++
> + drivers/regulator/Kconfig    |  1 +
>   include/linux/regmap.h       |  2 +-
> - 4 files changed, 22 insertions(+), 10 deletions(-)
> + 5 files changed, 23 insertions(+), 10 deletions(-)
>
>  --- a/drivers/base/regmap/Kconfig
>  +++ b/drivers/base/regmap/Kconfig
> @@ -96,6 +97,15 @@ Signed-off-by: Felix Fietkau <nbd at nbd.name>
>   postcore_initcall(regmap_initcall);
>  +
>  +MODULE_LICENSE("GPL");
> +--- a/drivers/regulator/Kconfig
> ++++ b/drivers/regulator/Kconfig
> +@@ -1,5 +1,6 @@
> + menuconfig REGULATOR
> +       bool "Voltage and Current Regulator Support"
> ++      select REGMAP

This will cause REGMAP to be included regardless if needed or not, but
would be acceptable (at least to me) as an interim build fix (most
targets using REGULATORs likely won't be part of the 4/32 gang
anyway).

The correct fix is likely to

a) add this REGMAP select to all REGULATOR drivers depending on/using
it (this can probably even be upstreamed)
b) (OpenWrt only) Change the usage in regulator/core.c and
regulator/helper.c to work like REGMAP is disabled if it is build as a
module.

b) is to allow building REGMAP as =m even when REGULATOR is enabled,
if no REGMAP requiring REGULATOR driver is enabled.


regards
Jonas

_______________________________________________
openwrt-devel mailing list
openwrt-devel at lists.openwrt.org
https://lists.openwrt.org/mailman/listinfo/openwrt-devel