linux-kernel - Re: [RFC PATCH v2 1/4] drm: Introduce generic probe function for component based masters.

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Message-ID: <20151019144225.GE13786@phenom.ffwll.local>
Date:	Mon, 19 Oct 2015 16:42:25 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Liviu Dudau <Liviu.Dudau@....com>, David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Mark Yao <mark.yao@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 1/4] drm: Introduce generic probe function for
 component based masters.

On Mon, Oct 19, 2015 at 02:26:38PM +0100, Russell King - ARM Linux wrote:
> On Mon, Oct 19, 2015 at 02:02:58PM +0100, Liviu Dudau wrote:
> > On Mon, Oct 19, 2015 at 01:25:37PM +0100, Russell King - ARM Linux wrote:
> > > Please don't move this into here, it's completely inappropriate.  Just
> > > because something makes use of this does not mean they only support
> > > 32-bit DMA.  Besides, this has nothing to do with whether or not it's
> > > OF-based or not.
> > 
> > Understood. My thinking process was that component-based drivers are all
> > OF-enabled (how else do you make use of the framework?) and 32-bit DMA is
> > present in 2 out of 3 drivers that are converted, so it looks to be common
> > enough that adding it to armada would not hurt. It was all done in the name of
> > collecting common code in a single function.
> 
> Which is an utterly crap reason.
> 
> It's also not appropriate.  I'm really not sure why you think that moving
> this here would in any way be appropriate - from my point of view, the
> mere proposal is utterly insane.
> 
> The "container" device does not do any DMA, so it's inappropriate for
> it to have DMA masks set or negotiated on it.  So, actually, no one
> should be setting the DMA mask for their container device.  It's wrong.

I think (and my opinion doesn't carry as much wheight here on dri-devel
than intel-gfx) the above is over the top bashing of a new contributor to
drm who really seems trying to do right. I think that's unecessary,
especially since you follow up with the reasonable reply below.

Thanks, Daniel

> What if we have a 64-bit OF based platform wanting to use the component
> helper, and they want to call this function?  You prevent them doing so
> by moving this into here, because they're then forced down to 32-bit DMA.
> Please, get rid of it, and leave this crappiness in the respective
> drivers.
> 
> -- 
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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