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From: Calum Mackay <>
To: Christoph Hellwig <>
Cc: Calum Mackay <>,,,
Subject: Re: [PATCH]  2.4: export the symbol "mmu_cr4_features" for XFree86 DRM kernel drivers
Date: Sat, 02 Aug 2003 12:54:25 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Christoph Hellwig wrote:
> Can you explain why they need it and why they magically need it
> because of vmap() ?

Sorry, of course.

[as Mitch has already pointed out privately] e.g the XFree86 DRM radeon 
Makefile includes this:


	# Check for 4-argument vmap() in some 2.5.x and 2.4.x kernels
	VMAP := $(shell grep -A1 'vmap.*count,$$' 
$(LINUXDIR)/include/linux/vmalloc.h | grep -c prot)

	ifneq ($(VMAP),0)

Christoph's vmap() backport introduced this reference in 
linux/vmalloc.h, so the DRM module is now compiled with VMAP_4_ARGS defined.

The radeon kernel driver source includes (via drm_memory.h) 
linux/vmalloc.h, iff VMAP_4_ARGS is defined. The latter includes (on 
i386) asm/asm-i386/pgtable.h, which includes asm/asm-i386/processor.h.

processor.h defines some inline functions [set_in_cr4() & 
clear_in_cr4()] which reference mmu_cr4_features.

mmu_cr4_features is currently declared in arch/i386/kernel/setup.c [and 
also arch/x86_64/kernel/setup.c] but not currently exported.

[The problem is not restricted to the radeon kernel driver; I've just 
used it as an example]


  reply	other threads:[~2003-08-02 11:55 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-08-01 12:52 [PATCH] 2.4: export the symbol "mmu_cr4_features" for XFree86 DRM kernel drivers Calum Mackay
2003-08-01 13:14 ` Christoph Hellwig
2003-08-02 11:54   ` Calum Mackay [this message]
2003-08-02 12:34     ` Calum Mackay

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