Message-ID: <4760727E.2090906@magtech.com.au>
Date: Thu, 13 Dec 2007 10:45:02 +1100
From: Aras Vaichas <arasv@magtech.com.au>
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Subject: mmaping an IO port device
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Hi,

Can I implement mmap with an io port connected device on an x86 based CPU?


Background:

I've got a device driver which can be compiled for either x86 or ARM. 
The driver provides an interface to an FPGA via either an IO port 
(0x180) on the x86 or as a memory mapped SRAM-like device (0x30000000) 
on the ARM.

To get myself an "address" for ioread calls I use:

FPGA_base = (u32) ioremap_nocache(FPGA_REG_IO_BASE, SZ_4K) for both CPU 
types.

FPGA_REG_IO_BASE is set to either 0x180 or 0x30000000 for x86 and ARM 
respectively.

I then call ioread16(FPGA_base + FPGA_register) for both x86 and ARM and 
it all works perfectly. No problems there.

My problem is that I am now moving from ioctl calls to a mmap interface. 
This isn't a problem with ARM as I can pass (0x30000000 >> PAGE_SHIFT) 
to remap_pfn_range() in the .mmap fops function but I can't pass 0x180 
because ... well, it's obvious.

Is there a trick?

Aras

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