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

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Message-ID: <20110316125138.GI2325@legolas.emea.dhcp.ti.com>
Date:	Wed, 16 Mar 2011 14:51:40 +0200
From:	Felipe Balbi <balbi@...com>
To:	Alexander Holler <holler@...oftware.de>
Cc:	Felipe Balbi <balbi@...com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: musb as module broken in 2.6.38

On Wed, Mar 16, 2011 at 12:21:38PM +0100, Alexander Holler wrote:
> 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.

yeah, just saw it. I need to fix up the musb_debug part... I guess there
was a patch making otg_state_string generic (as it should be) will get
that. I guess a fix for this can't come to -rc though, it would depend
on new features, unfortunately :-(

-- 
balbi
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