Date:	Sun, 8 Nov 2015 19:23:53 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 2/3] dmaselftest: add memcpy selftest support functions

On Sat, Nov 07, 2015 at 01:23:34AM -0500, Sinan Kaya wrote:
> 
> 
> On 11/5/2015 11:17 AM, Sinan Kaya wrote:
> >
> >
> >On 11/5/2015 7:05 AM, Vinod Koul wrote:
> >>On Wed, Nov 04, 2015 at 09:42:46PM -0500, Sinan Kaya wrote:
> >>>Here is what I proposed.
> >>>
> >>>- a common file that gets compiled into a module that wants to use
> >>>self-test with a public API. It can be called from driver's probe
> >>>routine.
> >>>- the test is independent of my implementation. It uses dmaengine
> >>>API and should be portable to most drivers.
> >>>- there *are* still drivers in the kernel that has selftest code
> >>>embedded inside them. I followed the design pattern from other
> >>>drivers thinking this must have been a good idea and it paid off for
> >>>me.
> >>>
> >>>As far as I understand, there is interest in doing more than this
> >>>and reusing the dmatest code for code duplication.
> >>
> >>the code that selftest uses to test will be very similar to dmatest code,
> >>both of these _should_ share this common code so that fixes get done for
> >>both!
> >>
> >
> >OK, I can move the code around and try to combine it if possible.
> >
> 
> I looked at this. IMO, merging selftest code and dmatest code is not
> a good idea.
> 
> Dmatest code has been well written and structured so that multiple
> DMA capabilities (XOR, PQ, MEMCPY) can be tested with the same code.
> 
> It supports threads and user space interaction.
> 
> The code I want to change (dmatest_func) is 3 levels deep in
> structure. My refactored code looked really ugly compared to the
> original code.

dmatest_func is still a bigger fn specific to dmatest. I was thinking that we
should have rather have two common functions
1) dmatest_do_dma() which does buffer allocation, invoking dmaengine APIs and
checking results, part of dmatest_func today

2) request_channels() would also be common along with cleanup routines

> >>>Facts:
> >>>- Dmatest can be actually configured to run during boot.
> >>>- Nobody besides the dma driver developer uses dmatest. This leaves
> >>>holes for regressions that are really hard to debug due to
> >>>interaction with the rest of the system.
> >>>- Dmatest doesn't exist in most distribution kernels.
> >>
> >>That doesn't mean it is not useful. This line of thought is not quite
> >>right.
> >>You are trying to say dmatest in not important and selftest is. Sorry but
> >>you are wrong, both are equally important and since both try to test
> >>and use
> >>similar routines (dmaengien API) they need to share the code and not
> >>duplicate it
> >>
> >>>If we want to do something else, I need clear directions. I can
> >>>remove the self test code completely from my driver. But, I need an
> >>>equivalent functionality.
> >>
> >>Add selftest to dmatest, we need both!
> >>
> >
> >OK, do you have any objections to compiling dmatest along with hidma in
> >the same module and calling a function from there ? or do you have
> >something else in your mind ?
Not the dmatest completely, that won't be right, but yes for the dmatest
core which is common b/w both. We cna put this is separate file to compile
along with driver if that is users requirement

-- 
~Vinod
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