Re: New kernel API for ROMs

Il Sat, Aug 07, 2004 at 07:59:29AM -0700, Jon Smirl ha scritto: 

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Maximum size of a standard PCI ROM is 128KB.

This is the maximun that kmalloc can allocate.

On non-x86 platforms the code will pick the length up from the size of
the PCI window. That window has no limit.

Hum, this is bad... what's the tipical size of video ROMs?

On the other hand, map_rom_copy is only called by the device driver for
a board that has minimal PCI decoding. The PCI spec allows the address
decoding for something like the ROM and framebuffer to be shared. A few
vendors have implemented this and the result is that you can't read the
ROM and framebuffer at the same time. This is why you need to make the
copy.  We only know of a couple PCI boards that have implemented this.

This memory is not performance critical and can be swapped, is there a
better way to allocate it?

Problem is that kmalloc may be unable to find many contiguous memory
pages.

You can check and see if the ROM is really big and use vmalloc, if not
then you use kmalloc (if I remember correctly my radeon has a 4KB ROM -
vmalloc would be overkill).

Luca
-- 
Home: http://kronoz.cjb.net
Ci sono due cose che l'uomo non puo` nascondere:
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