linux-kernel - RE: [PATCH 3/4 v2] i.MX31: framebuffer driver

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Message-ID: <Pine.LNX.4.64.0812101727270.4578@axis700.grange>
Date:	Wed, 10 Dec 2008 17:47:57 +0100 (CET)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Herring Robert <R.Herring@...escale.com>
cc:	linux-fbdev-devel@...ts.sourceforge.net, adaplas@...il.com,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH 3/4 v2] i.MX31: framebuffer driver

On Wed, 10 Dec 2008, Herring Robert wrote:

> You have obviously started with Freescale copyrighted GPL code, but you
> have not given credit or maintained our copyrights.

I did try to do this, at least in those files, which contain significant 
portions of Freescale code. If you feel that I missed it in some specific 
files please let me know, I'll happily add it, it was in no way my 
intension to steal the authorschip. E.g.:

> > diff --git a/drivers/video/mx3fb.c b/drivers/video/mx3fb.c
> > new file mode 100644
> > index 0000000..e8084ae
> > --- /dev/null
> > +++ b/drivers/video/mx3fb.c
> > @@ -0,0 +1,1843 @@
> > +/*
> > + * Copyright (C) 2008
> > + * Guennadi Liakhovetski, DENX Software Engineering, <lg@...x.de>
> > + *
> > + * Copyright 2004-2007 Freescale Semiconductor, Inc. All Rights Reserved.
...
> > +MODULE_AUTHOR("Freescale Semiconductor, Inc.");

...

>From IPU IDMAC driver:

diff --git a/drivers/mfd/ipu/ipu_idmac.c b/drivers/mfd/ipu/ipu_idmac.c
new file mode 100644
index 0000000..939acbf
--- /dev/null
+++ b/drivers/mfd/ipu/ipu_idmac.c
@@ -0,0 +1,1617 @@
+/*
+ * Copyright (C) 2008
+ * Guennadi Liakhovetski, DENX Software Engineering, <lg@...x.de>
+ *
+ * Copyright (C) 2005-2007 Freescale Semiconductor, Inc. All Rights Reserved.

Please tell me in which other files and in which form you'd like to see 
Freescale mentioned.

> The way you have structured the code moving the low-level SDC setup to
> the framebuffer will cause problems. There are lots of inter-module
> dependencies that have to be handled in the correct order to avoid
> hanging the h/w. For example, the SDC BG_EN has to be cleared before
> disabling the IDMA channel.

I tried to preserve the hardware handling code and the calling sequence. 
For example, I think, this is exactly what I do in this driver - 
sdc_disable_channel() first calls sdc_fb_uninit(), which clears the 
SDC_COM_FG_EN bit in SDC_COM_CONF, and then idmac_terminate_all() is 
called, which disables the IDMAC channel. Or have I understood you wrong?

> This structure will also not allow reuse of framebuffer, camera, and 
> v4l2 output drivers with the next version of h/w.

Why? All the generic (IDMAC, interrupt controller) code is put in a 
separate driver under drivers/mfd/ipu (see my patch 2/4), and only 
Synchronous Display Controller and Display Interface handling code is in 
the framebuffer driver. And the generic code is also used by the camera 
driver, whose second version is also going to be submitted to the V4L list 
soon. As for the "next version of h/w" - sorry, obviously I know nothing 
about it, so I cannot programme for it.

Besides, please understand, that I can develop and submit only parts that 
I test. Having no smart displays I cannot develop, test and submit 
Asynchronous Display Controller code, etc.

May I also note, that if Freescale made the effort and integrated their 
sources into the mainline, we wouldn't have this discussion now, the code 
would be structured the way you see best (as long as it is accepted by the 
maintainers) and would support any versions of hardware you like.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
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