Re: Framebuffer with banked memory

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 [off-list ref] a écrit : > On
Wed, 2002-10-30 at 18:49, alain volmat wrote:

quoted

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

quoted

framebuffer drivers ?? If so, what is the common
solution to do that ??

None in the current drivers.  

quoted

In fact the problem remains in the case of mmap

(which

quoted

is the most common ;( of course), since the memory
seams to be accessed directly by pointer, there

might

quoted

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

quoted

do that before the actual write at the end (even

if it

quoted

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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