From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 15 Sep 2006 18:40:06 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
MIME-Version: 1.0
Subject: Re: [Xenomai-core] 	[PATCH, RFC] Make ioremap'ed memory available
	through	rtdm_mmap_to_user()
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To: Stelian Pop <stelian.pop@domain.hid>
Cc: xenomai@xenomai.org

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Stelian Pop wrote:
> Hi,
>=20
> I need to be able to map an IO memory buffer to userspace from a RTDM
> driver.
>=20
> rtdm_mmap_to_user() seems to do what I need, but it doesn't work. Its
> code thinks that all virtual addresses between VMALLOC_START and
> VMALLOC_END are obtained through vmalloc() and tries to call
> xnarch_remap_vm_page() on them, which fails.

Ok, interesting (one never stops learning).

>=20
> Virtual addresses coming from ioremap() need to go through
> xnarch_remap_io_page_range(), and their physical address cannot be
> obtained with a simple virt_to_phys().
>=20
> A working patch is attached below, but there might (should ?) be a
> better way to do it. Some of the code may also belong to
> asm-generic/system.h instead of the RTDM skin.
>=20
> Note that you may also need to EXPORT_SYMBOL(vmlist and vmlist_lock) in=

> mm/vmalloc.c if you want to build the RTDM skin as a module.
>=20
> Comments ?

In case no one comes up with an easy, portable way to detect remapped
memory as well: What about some flags the caller of rtdm_mmap_to_user
has to pass, telling what kind of memory it is? Would simplify the RTDM
part, and the user normally knows quite well where the memory came from.
And I love to break APIs. :)

I'm CC'ing the first users of this service to ask for some feedback from
their POV. Hope gna does not -once again- mangles the CCs.

Jan


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