framebuffer driver as a module

framebuffer driver as a module

[Nikhil Jagtiani]

Hi,

I am running linux on an ipaq with framebuffer support. I need to enable
support for an external graphics card  through a pcmcia slot - the
driver for which does not exist.

As this is my first in terms of device driver writing, I would be
grateful for some advice.

Is it possible to write this additional driver as a dynamic kernel
module (along the lines of fbmem.c which is static), which however
itself implements all device specific functions? Can this  make use of
the same ioctl functions that fbmem.c uses (defined in fb.h)? Would
there be a conflict considering that fbmem would remain in the system?

Alternately if i am to write this as a static module (which loads onto
fbmem.c) - is there any way i could test it out without having to
recompile the kernel repeatedly?

Any other suggestions on how to proceed would be very welcome.

Many Thanks,

Nikhil Jagtiani



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Re: framebuffer driver as a module

[Petr Vandrovec]

On Fri, Aug 16, 2002 at 03:40:31PM -0700, Nikhil Jagtiani wrote:
> Hi,
> 
> I am running linux on an ipaq with framebuffer support. I need to enable
> support for an external graphics card  through a pcmcia slot - the
> driver for which does not exist.
> 
> As this is my first in terms of device driver writing, I would be
> grateful for some advice.
> 
> Is it possible to write this additional driver as a dynamic kernel
> module (along the lines of fbmem.c which is static), which however
> itself implements all device specific functions? Can this  make use of
> the same ioctl functions that fbmem.c uses (defined in fb.h)? Would
> there be a conflict considering that fbmem would remain in the system?

Couple of fbdevs can be compiled as a module, just look for tristate in
drivers/video/Config.in... You can insmod/rmmod such driver as you
want, only thing you must ensure is that there are no users of your
fbdev when you do rmmod. If you have two fbdevs, just move VTs from
"main" to "testing" and back by using con2fb/con2fbmap. If you'll have
only "testing" fbdev in your ipaq, and you have kernel with support
for virtual terminals, it is very tricky, usually impossible to unload
such module - it will have usecount 64 or 128 or another multiple of 64
as soon as you'll see 'Console: switching to ...' on your screen.
						Petr Vandrovec
						vandrove@vc.cvut.cz



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