Hello, ... BTW, here is a response from Antonino Daplas, to Linus's message, that Jon Smirl forwarded to the fbdev mailing list.
I think it doesn't make much sense to have such discution happening separatedly on two different mailing list, where most peoples involved only follow one of the two, so i forward the response from Antonino and also start a cross-thread (or whatever that is called). I hope it is ok for all of you. Friendly, Sven Luther ----- Forwarded message from Antonino Daplas <[EMAIL PROTECTED]> ----- On Sun, 2003-03-02 at 02:42, Jon Smirl wrote: > --- Linus Torvalds <[EMAIL PROTECTED]> wrote: > > From: Linus Torvalds <[EMAIL PROTECTED]> > > To: Keith Whitwell <[EMAIL PROTECTED]> > > CC: Jon Smirl <[EMAIL PROTECTED]>, Ian Romanick > > <[EMAIL PROTECTED]>, > > "DRI developer's list" > > <[EMAIL PROTECTED]> > > Subject: Re: [Dri-devel] future of DRI? > > Date: Sat, 1 Mar 2003 10:15:06 -0800 (PST) > > > > > > On Sat, 1 Mar 2003, Keith Whitwell wrote: > > > > > > Interesting you mention it. This is what Brian & > > I've done in the Mesa > > > embedded branch -- layered the radeon dri driver > > on top of fbdev. I can also > > > build regular DRI drivers from a minimal tree & > > sane set of makefiles. > > > > Personally, I'd rather see DRI _underneath_ fbdev > > rather than on top of. > > Since fbdev would require at least to know of (and > > obey) the DRI locking > > code - and would likely want to use all the same DRI > > command execution for > > things like blits etc (this is on the assumption > > that 2d and 3d will > > eventually use the same engine, which is probably a > > safe assumption). > > > > I _assume_ that what you really mean is that you use > > fbdev really only to > > set up the screen modes and do things like > > initialize the graphics > > buffers. > > > > Linus > > Yes, this is the sanest way. In my opinion, this is how fbdev and DRI should operate: 1. fbdev - provide a means to initialize and change the video state. - provide pointers to graphics/rendering memory, MMIO, DMA/ringbuffers - graphics memory may or may not be available to everyone, but the MMIO and command buffers will only be available to DRI - fbdev must not touch any registers besides those required to initialize the hardware. No 2D, no 3D. 2. fbaa - or framebuffer acceleration architecture or whatever you want to call it. This will be equivalent to Xfree86's XAA. It provides a 2D abstraction layer for clients residing in kernel space (ie fbcon). It will have software versions and optionally accelerated versions. The accelerated version has intimate knowledge of the 2D engine, but instead of accessing the hardware directly, it will rely on DRM to pass commands to the hardware. - in its current form, this will be the fb_imageblit(), fb_copyarea() and fb_fillrect(). 3. fbcon - this is the console driver that runs on top of fbaa 4. DRM - will get mmio pointer and command buffers from fbdev and will generally retain its original functions (interrupt handling, locking, arbitration, DMA interface, the works). It must also provide an interface for fbaa. 5. Userland apps - should only see the graphics memory pointer via fbdev. If they need to access the hardware, they have to go through DRM. Advantages: 1. fbdev will be secure. Without access to the MMIO regions, crashing the chipset is unlikely or at least difficult. Even malicious blit commands (blits to/from system memory) will not work. 2. Single point of entry for hardware access (DRI). You can run multiple clients trying to access the hardware simultaneously via DRM. And because of DRM's features, it will take care of command verification, arbitration, locking, context switching, etc. 3. Because DRM will handle both 2D and 3D and is pretty much the only one with hardware access, performance might actually increase. Disadvantages: 1. very linux specific. Xfree86 was designed to run on different platforms. Having one code for linux and another for the rest will be difficult for XFree86 developers to accept. 2. this will break fb-based apps that require chipset access, ie DirectFB. 3. a lot of code are difficult to implement in kernel space, ie initialization of secondary cards. Full video bios access can only be done, from a practical standpoint, in user space (the Intel 830, for instance, may require this). 4. Not all fbdev drivers has a DRI counterpart. For these chipsets, fbaa still has to access the hardware directly. In linux-2.5, fbcon is already separate from fbdev. Perhaps in 2.7, fbdev can be further reduced to a minimal core, moving the rest of the code to fbaa. Exporting the mmio regions to userland must be disallowed. Secondly, a module to access DRM services from within the kernel will be needed. Any comments? Tony ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Linux-fbdev-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/linux-fbdev-devel ----- End forwarded message ----- ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
