Re: Framebuffer with banked memory

["alain volmat" <avolmat@yahoo.fr>]

> The safest solution is to create custom fb_write?
> and fb_read? routines.
> Maybe James will add these hooks for hardware like
> yours.
> Then disallow mmap's except probably for the MMIO
> regions.
> 

What about adding fb_write / fb_read function in the
framebuffer (device dependant) driver. The same way as
for fb_mmap. I saw that at the beginning of fb_mmap in
fbmem.c, there is a test to see if the device driver
contains its own fb_mmap function, if so the device
driver fb_mmap will be used instead of the "generic"
fb_mmap. What about doing the same thing for fb_write
/ fb_read.

> PS:  What's your hardware?
Well actually it's a custom chip.

Alain

 --- Antonino Daplas <adaplas@pol.net> a écrit : > On
Wed, 2002-10-30 at 18:49, alain volmat wrote:
> > Hi,
> > 
> > As I said the video card I am now writing a
> > framebuffer for, doesn't have linear memory, which
> > means that I can only access a small part of the
> > memory at a time and then set offset registers in
> > order to access another part of the memory.
> > 
> > I would like to know if there is such case in
> current
> > framebuffer drivers ?? If so, what is the common
> > solution to do that ??
> None in the current drivers.  
> 
> > 
> > In fact the problem remains in the case of mmap
> (which
> > is the most common ;( of course), since the memory
> > seams to be accessed directly by pointer, there
> might
> > be no wait to detect if we need to set or not an
> > offset. In case of fb_read fb_write, it is
> possible to
> > do that before the actual write at the end (even
> if it
> > is not sooo beautiful ... ).
> The safest solution is to create custom fb_write?
> and fb_read? routines.
> Maybe James will add these hooks for hardware like
> yours.
> Then disallow mmap's except probably for the MMIO
> regions.
> 
> Creating a bank-switching mechanism, besides
> entailing a lot of work, is
> not entirely safe.
> 
> Tony
> 
> PS:  What's your hardware?
> 
> 
> 


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