<br><div><span class="gmail_quote">On 10/21/06, <b class="gmail_sendername">Ming Liu</b> <<a href="mailto:eemingliu@hotmail.com">eemingliu@hotmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Dear sudheer,<br>About the "mem=xx" argument, I checked it from the website and got such a<br>explanation:<br><br>This argument has several purposes: The original purpose was to specify the<br>amount of installed memory (or a value less than that if you wanted to
<br>limit the amount of memory available to linux).<br><br>From the argument above, it says "mem=xx" is to specify the amount of<br>memory available to Linux. I am not sure if I am right, but I think if I<br>use such an argument, that reserved part (that 5MB you mentioned), is not
<br>available any more for Linux to access it.<br><br>My original meaning is: specify a fixed physical address for a mount of<br>memory for reserved use. The point is to make this part of memory fixed in<br>the memory of physical address, and then another I/O peripheral could use
<br>DMA to access such a fixed physical address memory. However if I don't<br>reserve such a part, I must let Linux to allocate such a memory part. And<br>then Linux will not put it in a fixed physical address </blockquote>
<div><br>
yes <br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">and then the<br>peripheral will not know where is this part.</blockquote><div><br>
why do you think so ?<br>
Can't you give the physical address of the allocated memory from linux kernel to peripheral's DMA.?<br>
Unless you need to hardcode the physicall address i hope virt_to_phys(kmalloc_address) can be given to DMA.<br>
Sorry if i am still wrong in understanding your requirement.<br>
<br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Am I right? Thanks for your idea.<br><br>Also other ideas are appreciated.<br><br>
Regards<br>Ming<br><br>>Considering your setup as normal desktop, I hope this can be done by<br>>giving<br>>"mem= xxm" as the boot arguments. Say the dmesg in your system<br>>shows "<br>>495MB LOWMEM available." . In the boot arguments you can give
<br>>mem=490m<br>>saying the linux to use only 490MB . The rest 5MB can be used later<br>>as you<br>>wish.<br><br>_________________________________________________________________<br>享用世界上最大的电子邮件系统— MSN Hotmail。
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