From: davem@davemloft.net (David Miller)
To: linux-arm-kernel@lists.infradead.org
Subject: DMA using data buffer vmapped in kernel space
Date: Tue, 09 Mar 2010 02:20:15 -0800 (PST) [thread overview]
Message-ID: <20100309.022015.162981335.davem@davemloft.net> (raw)
In-Reply-To: <20100309101611.GC5691@n2100.arm.linux.org.uk>
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Tue, 9 Mar 2010 10:16:11 +0000
> It looks like the firmware interface may return a pointer to either the
> kernel binary itself for built-in firmware, or to a set of pages which
> have been vmap'd. In the former case, vmalloc_to_page() will fail.
Indeed, then you're right, the firmware layer would need to provide
the interface since only it knows where the memory is.
However, there's also no real portable way to compute physical
addresses from kernel image virtual addresses.
BTW, it's been my experience that drivers copy the firmware into a
locally allocated buffer exactly to avoid this problem.
WARNING: multiple messages have this Message-ID (diff)
From: David Miller <davem@davemloft.net>
To: linux@arm.linux.org.uk
Cc: mkl0301@gmail.com, thomas@koeller.dyndns.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: DMA using data buffer vmapped in kernel space
Date: Tue, 09 Mar 2010 02:20:15 -0800 (PST) [thread overview]
Message-ID: <20100309.022015.162981335.davem@davemloft.net> (raw)
In-Reply-To: <20100309101611.GC5691@n2100.arm.linux.org.uk>
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Tue, 9 Mar 2010 10:16:11 +0000
> It looks like the firmware interface may return a pointer to either the
> kernel binary itself for built-in firmware, or to a set of pages which
> have been vmap'd. In the former case, vmalloc_to_page() will fail.
Indeed, then you're right, the firmware layer would need to provide
the interface since only it knows where the memory is.
However, there's also no real portable way to compute physical
addresses from kernel image virtual addresses.
BTW, it's been my experience that drivers copy the firmware into a
locally allocated buffer exactly to avoid this problem.
next prev parent reply other threads:[~2010-03-09 10:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-04 21:11 DMA using data buffer vmapped in kernel space Thomas Koeller
2010-03-04 21:11 ` Thomas Koeller
2010-03-04 21:36 ` Russell King - ARM Linux
2010-03-04 21:36 ` Russell King - ARM Linux
2010-03-06 13:07 ` Thomas Koeller
2010-03-06 13:07 ` Thomas Koeller
2010-03-06 19:31 ` Russell King - ARM Linux
2010-03-06 19:31 ` Russell King - ARM Linux
2010-03-09 7:45 ` Lin Mac
2010-03-09 7:45 ` Lin Mac
2010-03-09 9:14 ` Russell King - ARM Linux
2010-03-09 9:14 ` Russell King - ARM Linux
2010-03-09 9:29 ` David Miller
2010-03-09 9:29 ` David Miller
2010-03-09 10:16 ` Russell King - ARM Linux
2010-03-09 10:16 ` Russell King - ARM Linux
2010-03-09 10:20 ` David Miller [this message]
2010-03-09 10:20 ` David Miller
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