From: "Daniel Glöckner" <daniel-gl@gmx.net>
To: Bob Liu <lliubbo@gmail.com>
Cc: linux-media@vger.kernel.org, dhowells@redhat.com,
linux-uvc-devel@lists.berlios.de, mchehab@redhat.com,
hverkuil@xs4all.nl, laurent.pinchart@ideasonboard.com,
sakari.ailus@maxwell.research.nokia.com,
martin_rubli@logitech.com, jarod@redhat.com, tj@kernel.org,
arnd@arndb.de, fweisbec@gmail.com, agust@denx.de, gregkh@suse.de,
vapier@gentoo.org
Subject: Re: [PATCH v3] media:uvc_driver: add uvc support on no-mmu arch
Date: Thu, 21 Apr 2011 11:47:43 +0200 [thread overview]
Message-ID: <20110421094743.GA8503@minime.bse> (raw)
In-Reply-To: <BANLkTimHX8aYoeSU1ES0Tw0Swaz9xYLt=Q@mail.gmail.com>
On Thu, Apr 21, 2011 at 04:20:36PM +0800, Bob Liu wrote:
> > on mmu systems do_mmap_pgoff contains a len = PAGE_ALIGN(len); line.
> > If we depend on this behavior, why not do it here as well and get rid
> > of the #ifdef?
> >
>
> If do it in do_mmap_pgoff() the whole system will be effected, I am
> not sure whether
> it's correct and needed for other subsystem.
With "here" I was referring to uvc_queue_mmap.
> >> + addr = (unsigned long)queue->mem + buffer->buf.m.offset;
> >> + ret = addr;
> >
> > Why the intermediate step using addr?
> >
>
> If don't return addr, do_mmap_pgoff() will return failure and we can't
> setup vma correctly.
> See mm/nommu.c line 1386(add = file->f_op->get_unmmapped_area() ).
I know, but why not do
ret = (unsigned long)queue->mem + buffer->buf.m.offset;
instead?
Daniel
next prev parent reply other threads:[~2011-04-21 9:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-21 3:17 [PATCH v3] media:uvc_driver: add uvc support on no-mmu arch Bob Liu
2011-04-21 7:59 ` Daniel Glöckner
2011-04-21 8:20 ` Bob Liu
2011-04-21 9:47 ` Daniel Glöckner [this message]
2011-04-21 9:57 ` Bob Liu
2011-04-21 10:06 ` Daniel Glöckner
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