linux-kernel - Re: [v4l-dvb-maintainer] bttv build error (CONFIG

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Date:	Thu, 01 Nov 2007 07:53:17 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
CC:	Trent Piepho <xyzzy@...akeasy.org>, v4l-dvb-maintainer@...uxtv.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [v4l-dvb-maintainer] bttv build error (CONFIG_NET=n)

Mauro Carvalho Chehab wrote:
> Randy,
> 
>>> The only reason the net stuff works, is because CONFIG_NET includes igmp.c,
>>> which can't be compiled as a module.  That means ip_compute_csum() will get
>>> pulled out of the lib.a file for igmp, and thus be present for the net modules
>>> that use it too.  If igmp could be turned off, made a module, or stopped using
>>> ip_compute_csum(), then the users of ip_compute_csum() that do depend on
>>> CONFIG_NET would have the same problem as bttv does.
>> Thanks for the analysis and summary.
>> (I'm still waiting for those lkml.org links to load... timed out)
>>
>>> It seems a shame to create a new ip checksum function in the bttv driver when
>>> a perfectly good one already exists and will already be present in just about
>>> every kernel out there.  Honestly, how common is NET=n and VIDEO_BT848=m
>>> outside of randconfig?
> 
> This might happen on embedded devices, like a set top box or a PVR,
> using a bttv hardware.
> 
>> so just adding "depends on NET" should be OK then?
> 
> Seems very weird to have bttv module dependent on NET, just because a
> checksum calculus function is defined there. 

Oh, I agree with that.  My comment above possibly needed a smiley.

> One possible solution would be to move this function to another place
> and having both NET, BTTV and other places selecting it.

I gave 3 possible solutions in the beginning email.  I would probably
just modify bttv to support osprey only when CONFIG_NET=y.

or fix the linking problem that Trent pointed out.

-- 
~Randy
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