linux-kernel - Re: [PATCH] Input: synaptics-rmi4

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Date:   Wed, 11 Jan 2017 16:39:07 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Duggan <aduggan@...aptics.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Christopher Heiny <cheiny@...aptics.com>,
        Nick Dyer <nick@...anahar.org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Lyude Paul <thatslyude@...il.com>
Subject: Re: [PATCH] Input: synaptics-rmi4 - make F03 a tristate symbol

On Tuesday, January 10, 2017 4:39:43 PM CET Andrew Duggan wrote:
> On 01/10/2017 04:16 AM, Arnd Bergmann wrote:
> > If CONFIG_INPUT=m, we get a build error for the rmi4-f03 driver,
> > added in linux-4.10:
> >
> > drivers/input/built-in.o: In function `rmi_f03_attention':
> > rmi_f03.c:(.text+0xcfe0): undefined reference to `serio_interrupt'
> > rmi_f03.c:(.text+0xd055): undefined reference to `serio_interrupt'
> > drivers/input/built-in.o: In function `rmi_f03_remove':
> > rmi_f03.c:(.text+0xd115): undefined reference to `serio_unregister_port'
> > drivers/input/built-in.o: In function `rmi_f03_probe':
> > rmi_f03.c:(.text+0xd209): undefined reference to `__serio_register_port'
> >
> > If we make the driver itself a 'tristate' instead of 'bool' symbol,
> > Kconfig ensures that it can only be a loadable module in this case,
> > which avoids the problem.
> 
> Unfortunately, the RMI4 driver does not support building the function 
> drivers as modules. If F03 is built as a module it will not be loaded by 
> the core. If we want f03 to be part of a module then rmi_core needs to 
> be built as a module. We should remove the module macros currently in 
> rmi_f03.c.
> 
> I was able to get a similar build error by setting CONFIG_RMI_CORE=y and 
> CONFIG_SERIO=m. Was CONFIG_RMI_CORE=y set when you encountered this 
> error? If so I think we should figure out a way to have Kconfig set 
> CONFIG_RMI_CORE=m if serio is built as a module.


Ok, I see what you mean now in 

static struct rmi_function_handler *fn_handlers[] = {
        &rmi_f01_handler,
#ifdef CONFIG_RMI4_F03
        &rmi_f03_handler,
#endif
#ifdef CONFIG_RMI4_F11
        &rmi_f11_handler,
#endif
...
};

I think we can actually make this more modular and more like other
drivers work:

If each of the sub-drivers gets changed to call
rmi_register_function_handler() on its own handler structure,
having some drivers as modules would just work.

It looks like the rmi_bus.c file was written to do it that way,
but for some reason the references to those drivers are all
in the same file.

	Arnd