Messages in this thread | ![/](/images/icornerl.gif) | | From | Geert Uytterhoeven <> | Date | Mon, 13 Mar 2017 13:46:16 +0100 | Subject | Re: [PATCH 2/2] [RFC] base: soc: Allow early registration of a single SoC device |
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Hi Arnd,
On Mon, Mar 13, 2017 at 1:41 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Thu, Mar 9, 2017 at 7:18 PM, Geert Uytterhoeven > <geert+renesas@glider.be> wrote: >> commit 1da1b3628df34a2a ("base: soc: Early register bus when needed") >> added support for early registration of SoC devices from a >> core_initcall(). However, some drivers need to check the SoC revision >> from an early_initcall(), which is even earlier. >> >> While registering the SoC bus and device, and using soc_device_match(), >> from an early_initcall() do work, the "soc" directory and the "soc0" >> file end up wrongly in the sysfs root, as the "bus" resp. "devices" >> directories haven't been created yet. >> >> To fix this, allow to register a single SoC device early on. >> As long as the SoC bus isn't registered, soc_device_match() just >> matches against this early device. >> When the SoC bus is registered later, the early device is registered for >> real. >> >> Note that soc_device_register() returns NULL (no error, but also not a >> valid pointer) when registering an early device. Hence platform devices >> cannot be instantiated as children of the "soc0" node representing an >> early SoC device. This should not be an issue, as that practice has >> been deprecated for new platforms. >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >> --- >> Is there a better way to fix this? >> While I believe all current users register a single SoC device, we may >> want to register multiple SoC devices in the future? >> >> soc_device_match() itself is completely independent from sysfs, but the >> sysfs operations are tied intimately to the driver core. >> >> The "bus" and "devices" directories are created from do_basic_setup() -> >> driver_init() -> devices_init() / buses_init(), which runs in between >> do_pre_smp_initcalls() (early_initcall()) and do_initcalls(). > > I'd prefer to not have to do the early registration at all and have fewer > special cases. Can you list a specific example that requires this?
The specific example is the Renesas R-Car SYSC driver, which manages PM Domains and thus needs to be initialized from an early_initcall.
> If we want to do early registration, then your implementation seems > fine to me.
Thanks!
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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
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