ioremap and outb

Arnd Bergmann arnd at
Fri Jan 4 21:45:20 EST 2008

On Friday 04 January 2008, Alessandro Rubini wrote:
> >          addr=ioremap(base_addr,size);          // Remap to Mem mapped
> Yes.

In newer drivers that are specific to powerpc, it's often easier
to use the of_iomap() function to map a device, so you don't
have to calculate the base address manually from the device tree.

> >          out_8(addr) and in_8(addr); 
> It should be right, although __raw_readb() and __raw_writeb() may
> suffice for you.

Actually not. While they may work, the __raw_* functions do not have
a specific meaning in device drivers. Depending on the I/O model, they
may or may not work on a given platform. The {in,out}_{8,{be,le}{16,32,64}}
functions however are defined to operate on local (not PCI) ioremapped
mmio devices, and are usually more efficient than the {read,write}{b,w,l,q}
variant you'd use on PCI devices.

	Arnd <><

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