RE: OMAP:DSS: possible bug in WAITFOR_VSYNC ioctl

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> -----Original Message-----
> From: Paul Mundt [mailto:lethal@xxxxxxxxxxxx]
> Sent: Tuesday, November 30, 2010 12:10 PM
> To: Ville Syrj?l?
> Cc: Hiremath, Vaibhav; M?ns Rullg?rd; linux-omap@xxxxxxxxxxxxxxx; linux-
> fbdev@xxxxxxxxxxxxxxx
> Subject: Re: OMAP:DSS: possible bug in WAITFOR_VSYNC ioctl
> 
> On Tue, Nov 30, 2010 at 03:34:40PM +0900, Paul Mundt wrote:
> > On Fri, Nov 26, 2010 at 02:55:39PM +0200, Ville Syrj?l? wrote:
> > > On Fri, Nov 26, 2010 at 05:38:11PM +0530, ext Hiremath, Vaibhav wrote:
> > > > With this finding, in case of OMAP3 we have to use OMAPFB_WAITFORGO
> > > > (breaking standard applications).
> > >
> > > Applications using the standard fbdev API won't work with manual
> update
> > > displays anyway. You need omapfb specific code to handle it so having
> > > another small difference is not a big deal.
> > >
> > > In DirectFB the that's trivial since there's already a simple omap
> > > gfxdriver where you could override the default flip functionality with
> > > WAITFORGO based stuff.
> > >
> > > Or, as I said, you could add another standard ioctl and fix up
> userspace
> > > to use it where appropriate and if the kernel driver supports it.
> > >
> > It seems like the WAITFORGO semantics could be layered on top of drivers
> > using deferred I/O pretty easily, but the question is whether this is
> > something that userspace plans to make general use of or not. If the
> only
> > user of it in userspace code is OMAP-specific, then there's probably not
> > a lot of point in moving it over to be generic, but if there are
> > sufficient cases where userspace cares about this information
> independent
> > of WAITFORVSYNC for manual update displays, then we can certainly look
> at
> > moving it over for those cases.
> 
> Also, WAITFORGO is a pretty abysmal name. It seems like what you want is
> a WAITFORHWSYNC or something similar.
[Hiremath, Vaibhav] Yes exactly, this name fits to the use-case and sounds ok to me. 

Tomi,
Any comments?

Thanks,
Vaibhav
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