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

-----Original Message-----
From: Tomi Valkeinen [mailto:tomi.valkeinen@nokia.com] 
Sent: Friday, May 14, 2010 6:32 PM
To: Guruswamy, Senthilvadivu
Cc: linux-omap@vger.kernel.org; linux-fbdev@vger.kernel.org; 
tony@atomide.com; Hiremath, Vaibhav
Subject: RE: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB

On Fri, 2010-05-14 at 12:03 +0200, ext Guruswamy, Senthilvadivu wrote:

quoted

quoted

-----Original Message-----
From: Tomi Valkeinen [mailto:tomi.valkeinen@nokia.com] 
Sent: Friday, May 14, 2010 12:54 PM
To: Guruswamy, Senthilvadivu
Cc: linux-omap@vger.kernel.org; linux-fbdev@vger.kernel.org; 
tony@atomide.com; Hiremath, Vaibhav
Subject: Re: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB

<snip>

quoted

quoted

The patch set makes VRFB optional. What happens if VRFB 

is turned off,

quoted

quoted

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 

quoted

explicitly. 
ie  config OMAP2_VRFB
	bool <No name given here>

Suppose on a build the user deliberately gives 

"CONFIG_OMAP2_VRFB not set",

quoted

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

quoted

as he has already deliberately changed the defconfig to say 

"VRFB not set".

quoted

The result of his experiment: No bootup on the board as the 

vaddr of VRFB 

quoted

is populated nor of the normal RAM buffer.

The kernel should be able to cope with that. While giving wrong boot
arguments to the kernel causing it to not boot is bad, it could be
somewhat acceptable. But if the user changes the rotation 
type via sysfs
file, and the kernel crashes (which is what I fear will happen), it's
totally unacceptable.

If it's possible to turn VRFB off, then the code should 
handle the case
where VRFB is not there. Meaning, returning error values or 
somehow else
failing gracefully, and informing the user of wrong arguments.

[Senthil] Yes, I could provide a check in the driver for wrong arguments.

 Tomi


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