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Re: [ppopov@mvista.com: Re: [Linux-mips-kernel]ioremap & ISA]

To: jim@jtan.com
Subject: Re: [ppopov@mvista.com: Re: [Linux-mips-kernel]ioremap & ISA]
From: Jun Sun <jsun@mvista.com>
Date: Tue, 18 Dec 2001 11:21:43 -0800
Cc: Ralf Baechle <ralf@oss.sgi.com>, linux-mips@oss.sgi.com
References: <20011217151515.A9188@neurosis.mit.edu> <20011217193432.A7115@dea.linux-mips.net> <20011218020344.A10509@neurosis.mit.edu> <20011218162506.A24659@dea.linux-mips.net> <20011218135712.B11726@neurosis.mit.edu>
Sender: owner-linux-mips@oss.sgi.com
Jim Paris wrote:
 
> How so?  See the memory map I just sent in my other mail.  Should I be
> adding isa_slot_offset to calls to check/request/release_mem_region?
> Or should I make a isa_{check,request,release}_mem_region that adds
> this in?  In which case, doesn't that turn /proc/iomem into a general
> memory map rather than an I/O memory map?
> 

My understanding is that it is from PCI memory space perspective.  System ram
is mapped at lower range.

> > > 4) it can use ioremap, and then read[bwl] and write[bwl] with the result
> > >  - this fails with the current ioremap; neither ioremap nor 
> > > read/write[bwl]
> > >    take isa_slot_offset into account
> >
> > And that's right because isa_slot_offset is used by the 
> > isa_{read,write}[bwl]
> > functions which do not require ioremap having been called before.  You're
> > (fortunately ...) using PCI and PCI drivers are required to use ioremap.
> 
> No, I'm not using PCI, but it's calling ioremap anyway.  So, yes, I
> suppose I could change the driver to not call ioremap and use
> isa_{read,write}[bwl] (since doing both adds KSEG1 twice).
> But why shouldn't ioremap + {read,write}[bwl] also work?
> If it did, I wouldn't have to touch the driver.

It seems like the driver assumes the ISA device is accessed through a PCI bus,
in which case the code would work.

Jun

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