From: Mukund JB. <muk...@es...> - 2005-03-07 13:36:05
|
Hi all, I also have a doubt regarding Accelarated Display driver.=20 Would u define an Accelerated display driver? Is it the driver to a Accelerated display card? Or Is it like accelerated display driver has a different meaning. I mean, it has the set features which will not be there on a normal driver for the same card? How can I implement a accelerated driver? Can I use the existing code of a framebuffer driver & do that? I heard in the groups saying framebuffer driver is not an accelerated driver.=20 Please take the pain of explaining how a framebuffer driver is different form accelerated driver? Regards, Mukund jampala |
From: Mukund JB. <muk...@es...> - 2005-03-07 18:07:33
|
Hello Burian, > The framebuffer implementation you get in the unofficial cirrus tree > (ep93xx-2.6) is not accelerated. The latest cirrus release (for > linux-2.4.21-rmk1) seems acclerated. Diff the source for details. >=20 > Note that the unaccelerated 2.6 driver and the accelerated > 2.4.21-rmk1-crus-whatever driver do not have a common anchestor, > the 2.6. was implemented from scratch, using fb-skeleton.c >=20 OK. > To explain it short: >=20 > if hardware acceleration is not available you'll have to emulate the > missing features in software (always possible), which is usually slow. Yes, right. This will be painful (performance wise). >=20 > if hardware acceleration is available but the driver does not use it > (emulates it as if it wasn't there) you still have a software-only driver. =20 You mean if the existing driver support is not accelerated, we need to emulate it in software again. But Why, can't we rewrite the driver at some places & make it work? > if hardware acceleration is available and the driver makes use of > it you've got a "accelerated" driver. In the ep93xx's case > the "raster engine" is used then. What is the raster engine? I goggled it, but did not find any thing strong enough. =20 My actual requirement is to rotate the screen by 90 degrees. Maillists ask me to use Xfree86 as it already has such kind of a support to rotate the screen.=20 Are there any side affects if I make use of the X server & rotate the screen. I mean is there any application that makes use of the video buffer directly without using X server and may fail to rotate the screen as we are rotating the screen at X server level and not at fb level. Also, if my device uses the console the screen rotation at X server level will not work. I mean if. Thanks & Regards, mukund jampala |
From: Antonino A. D. <ad...@ho...> - 2005-03-09 05:48:52
|
On Monday 07 March 2005 21:36, Mukund JB. wrote: > Hi all, > > I also have a doubt regarding Accelarated Display driver. > Would u define an Accelerated display driver? An accelerated driver means that most of the drawing is done by the GPU (the processor of the graphics card) while an unaccelerated driver implies that drawing is done by the main CPU. > > Is it the driver to a Accelerated display card? The driver is implementing the features of the card. > > Or > > Is it like accelerated display driver has a different meaning. I mean, > it has the set features which will not be there on a normal driver for > the same card? > The effect of software versus accelerated is the same. The main difference is that the GPU does the work if accelerated, the CPU if not. And the CPU version will be slower because it has to do other work besides drawing, and the data that is processed by the CPU has to go to and from the bus. The GPU has no such constraints. > How can I implement a accelerated driver? You need to know the details of the particular chipset you are working on. > Can I use the existing code of a framebuffer driver & do that? I heard Yes, if the framebuffer driver implements console acceleration. > in the groups saying framebuffer driver is not an accelerated driver. > Yes, the framebuffer driver only implements acceleration for the console. > Please take the pain of explaining how a framebuffer driver is different > form accelerated driver? Essentially, a framebuffer driver only exposes the video memory to its clients, period. You can read from or write to this memory, but you have to use the CPU to do this. In order to implement acceleration, you need to know how to talk to the GPU. Tony |