[Libdlo] [PATCH 2.6.32-rc7 1/1] udlfb: add dynamic modeset support

[Roberto De Ioris]

On Wed, 2009-11-25 at 16:58 -0800, Bernie Thompson wrote:
> Hi Roberto,
> 
> On the IOCTLs, do you think we could get rid of them entirely?
> 
> The IOCTL operations I see in displaylink-mod are:
>  A) blit and copy
>  B) set mode
>  C) return driver names
> 
> C is information queries that we could better expose through sysfs.  A
> and B mirror standard fbdev operations.
> 

The Xorg driver try to stay out of the fbdev implementation to gain best
performance. Probably it is not a good design choice, but displaylink
device need to fight with the relatively slow usb port. So at that time
it looks obvious to me that its better to break something than have a
slow driver.

> What kept the X server from using the starndard fbdev ops?  Is there
> anything that keeps us on the IOCTLs, if we update the X server to
> match?

Surely the B and C part could be removed, but an ioctl to force blitting
to the device is needed.


> * I realized that the new IOCTLs in the displaylink-mod codeline
> weren't about rendering operations (although the copy/flip blit was
> removed).  So my note that udlfb or udlfb+patch might have different
> performance from displaylink-mod wasn't right - theoretically, they
> should be the same.

Yeah, i think so, most of the displaylink-mod driver part are written
thinking about the X11 side


-- 
Roberto De Ioris
http://unbit.it
JID: roberto at jabber.unbit.it