RE: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB

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> -----Original Message-----
> From: Koen Kooi [mailto:koen@xxxxxxxxxxxxxxxxxxxxx] 
> Sent: Friday, May 14, 2010 4:09 PM
> To: Guruswamy, Senthilvadivu
> Cc: Tomi Valkeinen; linux-omap@xxxxxxxxxxxxxxx; 
> linux-fbdev@xxxxxxxxxxxxxxx; tony@xxxxxxxxxxx; Hiremath, Vaibhav
> Subject: Re: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB
> 
> 
> Op 14 mei 2010, om 12:03 heeft Guruswamy, Senthilvadivu het 
> volgende geschreven:
> 
> > 
> > 
> >> -----Original Message-----
> >> From: Tomi Valkeinen [mailto:tomi.valkeinen@xxxxxxxxx] 
> >> Sent: Friday, May 14, 2010 12:54 PM
> >> To: Guruswamy, Senthilvadivu
> >> Cc: linux-omap@xxxxxxxxxxxxxxx; linux-fbdev@xxxxxxxxxxxxxxx; 
> >> tony@xxxxxxxxxxx; Hiremath, Vaibhav
> >> Subject: Re: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB
> >> 
> >> Hi,
> >> 
> >> On Thu, 2010-05-13 at 17:20 +0200, ext Senthilvadivu 
> Guruswamy wrote:
> >>> From: Senthilvadivu Guruswamy  <svadivu@xxxxxx>
> >>> 
> >>> 
> >>> In this series, Kconfig is changed to have 
> >>> OMAP2_VRFB depend on ARCH_OMAP2 and ARCH_OMAP3.
> >>> This change takes care of the multi-omap builds. 
> >>> 
> >>> This patch would allow successful build of omap_4430sdp_defconfig 
> >>> when OMAP2_DSS and FB_OMAP2 is enabled from menuconfig.
> >>> 
> >>> List of Changed Files:
> >>> arch/arm/plat-omap/include/plat/vrfb.h
> >>> drivers/video/omap2/Kconfig
> >>> drivers/video/omap2/omapfb/Kconfig
> >> 
> >> The patch set makes VRFB optional. What happens if VRFB is 
> turned off,
> >> and the user uses VRFB for a framebuffer?
> > [Senthil] This patch keeps VRFB=y for ARCH_OMAP2 and ARCH_OMAP3.
> > User would have got an option to turn it OFF if it had appeared in 
> > the menuconfig selections.  I did not give that option in 
> menuconfig 
> > explicitly. 
> > ie  config OMAP2_VRFB
> > 	bool <No name given here>
> > 
> > Suppose on a build the user deliberately gives 
> "CONFIG_OMAP2_VRFB not set",
> > then VRFB functions are made as empty functions by the compiler.
> > 
> > This is fine as long as the user does not say omapfb.vrfb=1.
> > 
> > But if the user sets omapfb.vrfb=1, then it is a wrong 
> usage of the bootargs
> > as he has already deliberately changed the defconfig to say 
> "VRFB not set".
> > 
> > The result of his experiment: No bootup on the board as the 
> vaddr of VRFB 
> > is populated nor of the normal RAM buffer.
> 
> And that is unacceptable when working with customers (or 
> users in the open source world).  Instead of the kernel 
> hacker spending an hour or 2 on a proper solution we now need 
> to waste a whole lot more time supporting customers who pass 
> vrfb in bootargs without knowing that it's turned off in the kernel.
> 
> I suspect my viewpoint is skewed since I work in the field 
> with customers, instead of in the factory doing kernel work 
> (to use TI parlance).
> 
[Senthil] This error condition could occur only when the user does 
the settings wrong twice.  One time he is deliberately modifying the 
defconfig as "VRFB not set" even though menuconfig option is not given.  
Second he is contradicting himself by providing omapfb.vrfb=1.

If a build has to take care of this contradicting error scenarios
then my suggestion would be to add sdrc.o in arch/arm/mach-omap2,
even though it does not make sense to have an omap2-3 feature in the
omap4 and future omap defconfig builds.

Could you please share if you have thought of any other suggestion 
for this?

Regards,
Senthil--
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