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

From: "Guruswamy, Senthilvadivu" <svadivu@ti.com>
To: Tomi Valkeinen <tomi.valkeinen@nokia.com>
Cc: "linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
	"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
	"tony@atomide.com" <tony@atomide.com>,
	"Hiremath, Vaibhav" <hvaibhav@ti.com>
Subject: RE: [PATCH v2 0/2] DSS2:Allow FB to build without VRFB
Date: Mon, 17 May 2010 05:50:10 +0000	[thread overview]
Message-ID: <FCCFB4CDC6E5564B9182F639FC35608703042887E2@dbde02.ent.ti.com> (raw)
In-Reply-To: <1273842100.2814.85.camel@tubuntu.research.nokia.com>

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> -----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:
> > 
> > > -----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>
> 
> > > 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.
> 
> 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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