From: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Vinod Koul <vinod.koul@intel.com>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
linux-kernel@vger.kernel.org,
Jassi Brar <jassisinghbrar@gmail.com>,
Magnus Damm <magnus.damm@gmail.com>,
Paul Mundt <lethal@linux-sh.org>
Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()
Date: Fri, 16 Mar 2012 15:28:39 +0100 (CET) [thread overview]
Message-ID: <Pine.LNX.4.64.1203161522570.13465@axis700.grange> (raw)
In-Reply-To: <CACRpkdY7ApBc-gbSdf+=7PLtKSMvzYuBi7RNnVgi=vjcd-KvhQ@mail.gmail.com>
On Fri, 16 Mar 2012, Linus Walleij wrote:
> On Fri, Mar 16, 2012 at 12:09 PM, Guennadi Liakhovetski
> <g.liakhovetski@gmx.de> wrote:
>
> > And the least important question: who and when will implement the core
> > support for this?
>
> I'm trying to call the kernel HR department to hire a consultant for me but they
> just put me on the phone queue all the time, I don't know what I might be
> doing wrong ... :-)
>
> If the question is whether we need more people writing complicated core
> patches for the dmaengine I think the answer is "yes"?
>
> > 1. the client issues a dma_request_channel() with _just_ a capability mask
> > and a filter and its argument as parameters - _nothing_ about channel
> > restrictions.
> >
> > 2. you propose to eliminate a filter - the core has no way to know, which
> > channel to pick up...
>
> Nah, thinking about it...
>
> Eliminate the external filter, make it internal. We already have the
> problem that these filter functions need to be passed around too much
> in platform data e.g. so we need to do away with it.
>
> The filter functions seem to come from the DMA drivers
> themselves mostly. (Help me with the complete picture here...)
> For example:
>
> amba-pl08x.c:bool pl08x_filter_id(struct dma_chan *chan, void *chan_id)
> coh901318.c:bool coh901318_filter_id(struct dma_chan *chan, void *chan_id)
> pl330.c:bool pl330_filter(struct dma_chan *chan, void *param)
> sirf-dma.c:bool sirfsoc_dma_filter_id(struct dma_chan *chan, void *chan_id)
> ste_dma40.c:bool stedma40_filter(struct dma_chan *chan, void *data)
>
> So delete the typedef for dma_filter_fn remove these filters from
> external header files.
>
> And stop that thing from being passed around and into
> struct dma_device so the dmaengine core can still filter or process
> channels, but nothing on the outside need to know about it. That way
> we can centralize it to drivers/dma and not spread it out throughout
> the kernel.
>
> > 3. the wrapper, proposed by Russell, now calls dmaengine_slave_config(),
> > which fails, because that's a wrong channel (hope I get this right this
> > time - configuration has nothing to do with selection:-))
>
> Oh I was not thinking of relying on config to sort out channels.
>
> I was thinking of internalizing the dma_filter_fn and make it an
> (optional, maybe?) part of dmaengine.
Yessss!!! Let's do that! :-D Now, you're proposing exactly the same, as
what I was proposing! :-) Now you just have to remove the filter function
parameter from dma_request_channel() - it is anyway the same for all and
implemented in the dmaengine core - and you get
dma_request_channel(mask, slave_desc)
which is exactly what I was proposing! :-) Ok, I didn't remove the filter
function, instead I added one more parameter, but in essence - it is the
same! But since you yourself say, that this isn't easy - to remove the
filter function from all drivers at once, maybe my variant - add a
parameter and transition gradually - is easier! ;-)
Thanks
Guennadi
> > 4. that's it, if you start again - the dmaengine core will enumerate the
> > same channels again and propose the same unsuitable channel to you -
> > there's no way to continue to the next channel / device.
> >
> > What am I missing? How is the mapping going to be used, if you eliminate
> > the filter function?
>
> As above, I guess factoring away the filter functions would be
> the first real hard problem.
>
> Thanks,
> Linus Walleij
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
next prev parent reply other threads:[~2012-03-16 14:28 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-01 15:26 [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel() Guennadi Liakhovetski
2012-03-02 13:21 ` Guennadi Liakhovetski
2012-03-06 8:30 ` Vinod Koul
2012-03-06 8:53 ` Guennadi Liakhovetski
2012-03-06 12:08 ` Vinod Koul
2012-03-06 13:03 ` Guennadi Liakhovetski
2012-03-07 6:28 ` Vinod Koul
2012-03-07 9:18 ` Guennadi Liakhovetski
2012-03-07 9:30 ` Russell King - ARM Linux
2012-03-07 9:55 ` Linus Walleij
2012-03-07 10:02 ` Guennadi Liakhovetski
2012-03-07 10:31 ` Russell King - ARM Linux
2012-03-07 12:30 ` Guennadi Liakhovetski
2012-03-07 12:45 ` Guennadi Liakhovetski
2012-03-07 12:46 ` Russell King - ARM Linux
2012-03-07 13:49 ` Guennadi Liakhovetski
2012-03-07 14:26 ` Russell King - ARM Linux
2012-03-07 15:44 ` Guennadi Liakhovetski
2012-03-07 16:27 ` Russell King - ARM Linux
2012-03-07 18:21 ` Guennadi Liakhovetski
2012-03-08 6:30 ` Vinod Koul
2012-03-08 10:16 ` Guennadi Liakhovetski
2012-03-08 10:55 ` Vinod Koul
2012-03-08 11:22 ` Guennadi Liakhovetski
2012-03-08 11:34 ` Vinod Koul
2012-03-08 12:58 ` Vinod Koul
2012-03-08 13:18 ` Guennadi Liakhovetski
2012-03-09 9:21 ` Vinod Koul
2012-03-09 9:24 ` Guennadi Liakhovetski
2012-03-09 9:39 ` Vinod Koul
2012-03-09 12:20 ` Guennadi Liakhovetski
2012-03-09 14:07 ` Russell King - ARM Linux
2012-03-09 14:15 ` Guennadi Liakhovetski
2012-03-12 2:47 ` Vinod Koul
2012-03-12 19:47 ` Linus Walleij
2012-03-16 9:36 ` Guennadi Liakhovetski
2012-03-16 10:16 ` Linus Walleij
2012-03-16 10:31 ` Russell King - ARM Linux
2012-03-16 11:09 ` Guennadi Liakhovetski
2012-03-16 14:11 ` Linus Walleij
2012-03-16 14:28 ` Guennadi Liakhovetski [this message]
2012-03-30 5:44 ` Linus Walleij
2012-03-30 6:40 ` Guennadi Liakhovetski
2012-03-30 10:38 ` Russell King - ARM Linux
2012-04-03 20:36 ` Linus Walleij
2012-04-03 20:44 ` Linus Walleij
2012-04-12 21:33 ` Guennadi Liakhovetski
2012-04-12 23:48 ` Russell King - ARM Linux
2012-03-30 10:29 ` Russell King - ARM Linux
2012-03-30 10:40 ` Guennadi Liakhovetski
2012-03-30 10:43 ` Russell King - ARM Linux
2012-03-19 11:58 ` Vinod Koul
2012-03-30 10:25 ` Russell King - ARM Linux
2012-03-19 11:39 ` Vinod Koul
2012-03-19 11:37 ` Vinod Koul
2012-03-19 11:47 ` Guennadi Liakhovetski
2012-03-19 13:34 ` Vinod Koul
2012-03-19 13:38 ` Guennadi Liakhovetski
2012-03-19 14:00 ` Vinod Koul
2012-03-19 14:09 ` Guennadi Liakhovetski
2012-03-19 14:22 ` Vinod Koul
2012-03-19 14:45 ` Guennadi Liakhovetski
2012-03-19 16:20 ` Vinod Koul
2012-03-19 16:32 ` Guennadi Liakhovetski
2012-03-20 7:11 ` Vinod Koul
2012-03-08 11:46 ` Linus Walleij
2012-03-08 12:36 ` Guennadi Liakhovetski
2012-03-07 16:31 ` Linus Walleij
2012-03-07 16:20 ` Linus Walleij
2012-03-07 9:46 ` Linus Walleij
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