XFree86-FBDev and /dev/fb0

XFree86-FBDev and /dev/fb0

[Jiri Kastner jr.]

I have installed XFree86-FBDev, but everytime, when I want to start X, I get
message, that is missing /dev/fb0, and I dont know, how to make it (MAKEDEV
dont know anything about fb* devices).

Jiri Kastner.

Re: XFree86-FBDev and /dev/fb0

[Eric Kimminau]

"Jiri Kastner jr." wrote:
> 
> I have installed XFree86-FBDev, but everytime, when I want to start X, I get
> message, that is missing /dev/fb0, and I dont know, how to make it (MAKEDEV
> dont know anything about fb* devices).
> 
> Jiri Kastner.

You have to enable it in your kernel. 
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Re: XFree86-FBDev and /dev/fb0

[Jiri Kastner jr.]

Dne Ut, 04 jan 2000 jste napsal(a):
 
> You have to enable it in your kernel. 

I have kernel with framebuffer (when I boot, I see linux-sgi.logo - 2.2.1)

I have no /dev/fb0.

Jiri Kastner

Re: XFree86-FBDev and /dev/fb0

[Andy Isaacson]

On Wed, Jan 05, 2000 at 04:06:24PM +0100, Jiri Kastner jr. wrote:
> Dne Ut, 04 jan 2000 jste napsal(a):
>  
> > You have to enable it in your kernel. 
> 
> I have kernel with framebuffer (when I boot, I see linux-sgi.logo - 2.2.1)
> 
> I have no /dev/fb0.

You probably need to create the device node, then.  Look at the man
page for mknod, and Documentation/devices.txt in your kernel source
tree, for further info.

-andy
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Re: XFree86-FBDev and /dev/fb0

[Ralf Baechle]

On Wed, Jan 05, 2000 at 11:49:22AM -0500, Andy Isaacson wrote:

> > I have kernel with framebuffer (when I boot, I see linux-sgi.logo - 2.2.1)
> > 
> > I have no /dev/fb0.
> 
> You probably need to create the device node, then.  Look at the man
> page for mknod, and Documentation/devices.txt in your kernel source
> tree, for further info.

That alone won't help.

A system with the XL graphics will never have a real working framebuffer.

  Ralf

Re: XFree86-FBDev and /dev/fb0

[William J. Earl]

Ralf Baechle writes:
 > On Wed, Jan 05, 2000 at 11:49:22AM -0500, Andy Isaacson wrote:
 > 
 > > > I have kernel with framebuffer (when I boot, I see linux-sgi.logo - 2.2.1)
 > > > 
 > > > I have no /dev/fb0.
 > > 
 > > You probably need to create the device node, then.  Look at the man
 > > page for mknod, and Documentation/devices.txt in your kernel source
 > > tree, for further info.
 > 
 > That alone won't help.
 > 
 > A system with the XL graphics will never have a real working framebuffer.

     Since the real graphics framebuffer is in memory which is not addressable
by the processor, the only way to fake a CPU-addressable framebuffer is
to reserve a chunk of main memory, and then DMA the contents into the
real framebuffer when the CPU-addressable framebuffer is changed (or
every vertical refresh interval, if there is no way to tell when the buffer
changes).  You could probably play with the PTE valid and mod bits to detect
when pages are changed.  It would in any case be relatively inefficient
compared to using the graphics pipeline as intended, since uncached writes
to the graphics pipeline are pretty cheap (better than cached or uncached
writes to large areas of main memory).

Re: XFree86-FBDev and /dev/fb0

[Andy Isaacson]

On Wed, Jan 05, 2000 at 04:55:22PM -0800, William J. Earl wrote:
> Ralf Baechle writes:
>  > A system with the XL graphics will never have a real working framebuffer.
> 
>      Since the real graphics framebuffer is in memory which is not addressable
> by the processor, the only way to fake a CPU-addressable framebuffer is
> to reserve a chunk of main memory, and then DMA the contents into the
> real framebuffer when the CPU-addressable framebuffer is changed (or
> every vertical refresh interval, if there is no way to tell when the buffer
> changes).  You could probably play with the PTE valid and mod bits to detect
> when pages are changed.  It would in any case be relatively inefficient
> compared to using the graphics pipeline as intended, since uncached writes
> to the graphics pipeline are pretty cheap (better than cached or uncached
> writes to large areas of main memory).

XFree86 has builtin support for this mode of operation in the latest
development snapshot (3.9.17).  They call it ShadowFB.  Of course that
would only work in X, not on console.  Apparently it's fairly easy to
write a driver that supports ShadowFB; all you have to be able to do
is update a rectangular area of the screen on demand.

-andy
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Re: XFree86-FBDev and /dev/fb0

[Ulf Carlsson]

> On Wed, Jan 05, 2000 at 04:55:22PM -0800, William J. Earl wrote:
> > Ralf Baechle writes:
> >  > A system with the XL graphics will never have a real working framebuffer.
> > 
> >      Since the real graphics framebuffer is in memory which is not addressable
> > by the processor, the only way to fake a CPU-addressable framebuffer is
> > to reserve a chunk of main memory, and then DMA the contents into the
> > real framebuffer when the CPU-addressable framebuffer is changed (or
> > every vertical refresh interval, if there is no way to tell when the buffer
> > changes).  You could probably play with the PTE valid and mod bits to detect
> > when pages are changed.  It would in any case be relatively inefficient
> > compared to using the graphics pipeline as intended, since uncached writes
> > to the graphics pipeline are pretty cheap (better than cached or uncached
> > writes to large areas of main memory).
> 
> XFree86 has builtin support for this mode of operation in the latest
> development snapshot (3.9.17).  They call it ShadowFB.  Of course that
> would only work in X, not on console.  Apparently it's fairly easy to
> write a driver that supports ShadowFB; all you have to be able to do
> is update a rectangular area of the screen on demand.

Yeah, and that's what I tried to get working but I ran into other problems with
the dynamic loading of X modules and stuff so I never got the chance to
concentrate on the driver.  I have the early stages of a driver around though.

Ulf

Re: XFree86-FBDev and /dev/fb0

[Andy Isaacson]

On Wed, Jan 05, 2000 at 05:27:33PM -0800, Ulf Carlsson wrote:
> > XFree86 has builtin support for this mode of operation in the latest
> > development snapshot (3.9.17).  They call it ShadowFB.  Of course that
> > would only work in X, not on console.  Apparently it's fairly easy to
> > write a driver that supports ShadowFB; all you have to be able to do
> > is update a rectangular area of the screen on demand.
> 
> Yeah, and that's what I tried to get working but I ran into other problems with
> the dynamic loading of X modules and stuff so I never got the chance to
> concentrate on the driver.  I have the early stages of a driver around though.

You're probably the first person to try the XFree86 loader code on
MIPS so it's not suprising you had trouble.  Try putting
"#define DoLoadableServer NO" in xc/config/cf/host.def; that way it'll
not try to use the loader at all.

-andy
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Re: XFree86-FBDev and /dev/fb0

[M. Adam Kendall]

On 06-Jan-2000 Ulf Carlsson wrote:
> Yeah, and that's what I tried to get working but I ran into other problems
> with
> the dynamic loading of X modules and stuff so I never got the chance to
> concentrate on the driver.  I have the early stages of a driver around
> though.

And is this code available anywhere?  I noticed that the FTP and web
servers are terribly out of date.  Is everyone keeping their own separate
copies of code for the MIPS/Indy platform, or am I just not looking in the
right places?

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