<html><body bgcolor="#FFFFFF"><div><div><br><br>在 2012-7-10，17:16，"Prabhu nath" <<a href="mailto:gprabhunath@gmail.com"><a href="mailto:gprabhunath@gmail.com">gprabhunath@gmail.com</a></a>> 写道：<br><br></div><div></div><blockquote type="cite"><div>Thanks for your reply. Plz see inline<br><br><div class="gmail_quote">On Tue, Jul 10, 2012 at 11:17 AM, Philipp Ittershagen <span dir="ltr"><<a href="mailto:p.ittershagen@googlemail.com" target="_blank"></a><a href="mailto:p.ittershagen@googlemail.com"><a href="mailto:p.ittershagen@googlemail.com">p.ittershagen@googlemail.com</a></a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Prabhu,<br>
<div class="im"><br>
On Tue, Jul 10, 2012 at 6:56 AM, Prabhu nath <<a href="mailto:gprabhunath@gmail.com"></a><a href="mailto:gprabhunath@gmail.com"><a href="mailto:gprabhunath@gmail.com">gprabhunath@gmail.com</a></a>> wrote:<br>
> For E.g. I have a device whose physical address range is 0x80008000 to<br>
> 0x80008FFF.<br>
> Is it possible to map this device physical address to a known<br>
> virtual address range 0xF0008000 to 0xF0008FFF.<br>
<br>
</div>I don't think this is possible, because these virtual address ranges<br>
are handled by the kernel VMA system and are allocated dynamically, so<br>
that is not just a bitmask or something to change.<br>
<div class="im"><br>
> My hardware configuration has 128 MB of system RAM which will have been<br>
> MAPPED to the Kernel virtual address from 0xC0000000 to 0xC7FFFFFF<br>
><br>
> Also is it possible to configure the vmalloc kernel virtual address region<br>
> to a fixed range of 128 MB from 0xC8000000 to 0xCFFFFFFF<br>
<br>
</div>You could change PAGE_OFFSET. From [1]:<br>
<br>
<br>
PHYS_OFFSET<br>
Physical start address of the first bank of RAM.<br>
<br>
PAGE_OFFSET<br>
Virtual start address of the first bank of RAM. During the kernel<br>
boot phase, virtual address PAGE_OFFSET will be mapped to physical<br>
address PHYS_OFFSET, along with any other mappings you supply.<br>
This should be the same value as TASK_SIZE.<br>
<br>
<br>
But I'm curious: Why do you want to change it?<br></blockquote><div><br></div><div> Just wanted to have a constant mapping from PA to VA of devices and wanted to have a separate region for vmalloc. </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br></blockquote></div></div></blockquote><div><br></div><div>what do you mean constant?</div><div>After mapping, it is constant.</div><div>Before mapping, it is constant for </div><div>Low memory region, but is not </div><div>Constant for vmalloc region. </div><div><br></div><div>Vmalloc region is separate in default.</div><div>Your change doesn't make any sense.</div><div><br></div><div>The most difficult thing for you is</div><div>To make sure what do you want to</div><div>Do really. Please give detail demand.</div><div><br></div><br><blockquote type="cite"><div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Greetings,<br>
<br>
Philipp<br>
<br>
<br>
[1]: <a href="http://www.kernelport.org/defines.html" target="_blank"></a><a href="http://www.kernelport.org/defines.html"><a href="http://www.kernelport.org/defines.html">http://www.kernelport.org/defines.html</a></a><br>
</blockquote></div><br>
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