From mboxrd@z Thu Jan 1 00:00:00 1970 From: pavel@ucw.cz (Pavel Machek) Date: Wed, 3 May 2017 21:58:29 +0200 Subject: [patch] autogain support for bayer10 format (was Re: [patch] propagating controls in libv4l2) In-Reply-To: <20170503190556.GT23750@n2100.armlinux.org.uk> References: <20170419105118.72b8e284@vento.lan> <20170424093059.GA20427@amd> <20170424103802.00d3b554@vento.lan> <20170424212914.GA20780@amd> <20170424224724.5bb52382@vento.lan> <20170426105300.GA857@amd> <20170426081330.6ca10e42@vento.lan> <20170426132337.GA6482@amd> <20170503190556.GT23750@n2100.armlinux.org.uk> Message-ID: <20170503195829.GA17315@amd> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed 2017-05-03 20:05:56, Russell King - ARM Linux wrote: > On Wed, Apr 26, 2017 at 06:43:54PM +0300, Ivaylo Dimitrov wrote: > > >+static int get_luminosity_bayer10(uint16_t *buf, const struct v4l2_format *fmt) > > >+{ > > >+ long long avg_lum = 0; > > >+ int x, y; > > >+ > > >+ buf += fmt->fmt.pix.height * fmt->fmt.pix.bytesperline / 4 + > > >+ fmt->fmt.pix.width / 4; > > >+ > > >+ for (y = 0; y < fmt->fmt.pix.height / 2; y++) { > > >+ for (x = 0; x < fmt->fmt.pix.width / 2; x++) > > > > That would take some time :). AIUI, we have NEON support in ARM kernels > > (CONFIG_KERNEL_MODE_NEON), I wonder if it makes sense (me) to convert the > > above loop to NEON-optimized when it comes to it? Are there any drawbacks in > > using NEON code in kernel? > > Using neon without the VFP state saved and restored corrupts userspace's > FP state. So, you have to save the entire VFP state to use neon in kernel > mode. There are helper functions for this: kernel_neon_begin() and > kernel_neon_end(). ... > Given that, do we really want to be walking over multi-megabytes of image > data in the kernel with preemption disabled - it sounds like a recipe for > a very sluggish system. I think this should (and can only sensibly be > done) in userspace. The patch was for libv4l2. (And I explained why we don't need to overoptimize this.) Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 181 bytes Desc: Digital signature URL: