linux-kernel - Re: musb as module broken in 2.6.38

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Message-ID: <4D809D42.7000102@ahsoftware.de>
Date:	Wed, 16 Mar 2011 12:21:38 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Felipe Balbi <balbi@...com>
CC:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: musb as module broken in 2.6.38

Am 16.03.2011 11:48, schrieb Felipe Balbi:
> Hi,
>
> On Mar 16, 2011, at 12:43 PM, Alexander Holler wrote:
>
>> Am 16.03.2011 11:38, schrieb Felipe Balbi:
>>> hi,
>>>
>>> On Mar 16, 2011, at 12:30 PM, Alexander Holler wrote:
>>>> Am 16.03.2011 11:24, schrieb Felipe Balbi:
>>>>> Hi,
>>>>>
>>>>> On Mar 16, 2011, at 12:17 PM, Alexander Holler wrote:
>>>>>>> static int __init omap2430_probe(struct platform_device *pdev)
>>>>>>
>>>>>> Neither omap2430_init() nor omap2430_probe() will be called here.
>>>>>
>>>>> and why is that ? It's even in sysfs already:
>>>>>
>>>>>>>> beagle linux # ls /sys/devices/platform/ | grep musb
>>>>>>>> musb-omap2430
>>>>
>>>> Don't know, I haven't written or changed the driver. ;)
>>>
>>> hehe, Just thought that you had something in mind already.
>>>
>>> probe() functions are called when, in case of platform_devices,
>>> the name matches with driver name. musb-omap2430 platform_device
>>> is allocated in arch/arm/mach-omap2/usb-musb.c, then musb-2430
>>> driver lives in drivers/usb/musb/omap2430.c. musb-2430 allocates a
>>> platform_device for musb-hdrc core driver.
>>>
>>> We did that because the same core is used in many different platforms
>>> (OMAP, discrete chips, ST-Ericsson, DaVinci, PCI cards, etc) so we
>>> needed to "abstract" platform-specific details such as clock handling
>>> and power management.
>>>
>>> There's still work to be done, for sure, e.g. the DMA part is still quite
>>> screwed up, but the drivers are correctly named which means they
>>> should be matching and probing. Now, musb-hdrc isn't probing, as
>>> you say, and I'd like to know why. I'll try to spend some time in
>>> it when I get back to the office.
>>
>> I currently assume it's something with
>>
>> subsys_initcall(omap2430_init);
>>
>> Have to read about subsys_initcall() and why omap2430_init isn't called here.
>
> I guess I know what the problem is. If you search for omap2430_init
> in vmlinux it won't be there. I guess when a directory is marked as
> obj-m, Kbuild won't search for symbols to be statically linked to vmlinux
> on that directory. Since we use the same Kconfig entry to select musb as
> module and include drivers/usb/musb directory into build system, we
> are falling into that case.
>
> Try changing drivers/usb/musb to obj-y in drivers/Makefile and see if things
> start working.

Thanks, seems to be the right way, but doesn't work without more 
changes. I get some undefined references e.g. to stuff in musb_core.c 
and musb_debug (otg_state_string and musb_debug). I assume it's because 
musb_core and musb_debug are part of the module musb_hdrc.

Regards,

Alexander Holler
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