From: David Woodhouse <dwmw2@infradead.org>
To: Mike Frysinger <vapier.adi@gmail.com>
Cc: David Howells <dhowells@redhat.com>,
Linux kernel mailing list <linux-kernel@vger.kernel.org>,
uclinux-dist-devel <uclinux-dist-devel@blackfin.uclinux.org>
Subject: Re: userspace firmware loader, vmap, and nommu
Date: Tue, 06 Oct 2009 05:38:59 +0100 [thread overview]
Message-ID: <1254803939.14541.49.camel@macbook.infradead.org> (raw)
In-Reply-To: <8bd0f97a0910052125m4327fef3i47e3b549938802f9@mail.gmail.com>
On Tue, 2009-10-06 at 00:25 -0400, Mike Frysinger wrote:
> semi-recently (9 Apr 2009), the userspace firmware code was rewritten
> to use vmap(). this causes problems for nommu systems as it isnt
> possible to create a virtually contiguous map with physically
> discontiguous pages.
Oops, sorry.
> the firmware loader used to work before this
> change because it would handle the realloc steps itself (allocate
> larger contiguous memory, copy over older data, release older memory)
> and vmalloc() on nommu is simply kmalloc().
>
> this could be handled transparently on nommu systems by moving this
> scatter gathering of pages into vmap:
> void *vmap(struct page **pages, unsigned int count, unsigned long
> flags, pgprot_t prot)
> {
> unsigned int i;
> void *new_map, *page_data;
>
> new_map = kmalloc(count << PAGE_SHIFT, GFP_KERNEL);
> if (!new_map)
> return NULL;
>
> for (i = 0; i < count; ++i) {
> page_data = kmap(pages[i]);
> memcpy(new_map + (i << PAGE_SHIFT), page_data, PAGE_SIZE);
> kunmap(page_data);
> }
>
> return new_map;
I wouldn't necessarily want to do that for _all_ vmap() calls, but doing
it just for the firmware loader might make some sense. It does mean you
have to have _twice_ as much memory available as the size of the
firmware in question. And you have to have a contiguous chunk even
_after_ allocating it once piecemeal.
> void vunmap(const void *addr)
> {
> kfree(addr);
> }
>
> or we could add nommu-specific code to the firmware loader to not use
> vmap(). how would you like to go David (Howells) ?
Or we could add _generic_ code not to use vmap(). Just teach the users
that you don't get a virtually contiguous blob back from
request_firmware(); you get an array of pages instead.
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@intel.com Intel Corporation
next prev parent reply other threads:[~2009-10-06 4:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-06 4:25 userspace firmware loader, vmap, and nommu Mike Frysinger
2009-10-06 4:38 ` David Woodhouse [this message]
2009-10-06 4:56 ` Mike Frysinger
2009-12-21 16:44 ` [PATCH] nommu: implement vmap/vunmap with kmalloc Mike Frysinger
2010-01-07 6:49 ` [uClinux-dev] " Mike Frysinger
2010-03-09 16:11 ` [PATCH v2] NOMMU: " Mike Frysinger
2010-03-31 17:11 ` David Howells
2010-03-31 19:54 ` Mike Frysinger
2010-03-31 23:06 ` David Howells
2010-03-31 23:07 ` David Howells
2010-03-31 23:10 ` Mike Frysinger
2010-01-16 15:57 ` [PATCH] nommu: " David Howells
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