So, I have the address of the memory address and I want to map it into my kernels memory space, so that I can access the memory for both reading and writing. I am not very good at doing this. I have been reading up a C pointers but for some reason I don't think that is all I need. I have been working with another member here with bitwise shifts and masking, so that I understand; however, my trouble is that I don't fully understand how to map the memory for usage. Any help?
Address of the memory address? You mean the address of a pointer which contains a memory address?
What OS are you using? Linux I suppose?
If you want to allocate memory for the kernel you can use kmalloc() for example in linux.
If you want to allocate a specific memory location then... dunno. I can't think of a reason you would want to to this either.
No, I mean the address of a space of memory belonging to a device on the PCI bus. From the PCI controller I was given the IO and Memory space addresses of a device I am coding for and I now need to map the memory space address so that I can read/write to and from it. Any ideas? I was thinking to kmalloc a struct but not sure how that actually maps the memory space for access.
Last edited by jacob12; 10-04-2008 at 07:34 AM.
Dunno exactly. You could use copy_from(to)_user maybe and use that data, but I guess you don't want that because of efficiency.
Other functions that I found with a google search:
iorempa(), mmap(), kmap()
See the Linux Reference says that I could access the device three ways:
01. Memory Locations
02. I/O Ports
03. Config Registers
I was trying the Config Registers method but I kept returning garbage. I would write 003F0000 to Offset 0x90 of the Base 5 Memory Space Address and my return would be 00700000. I made sure the IO Enabled bits were set to 00000011 which enables IO and Memory Access, but I never checked it after, I'll try that to see if it got set; however assuming it had I am still returning garbage. I might try the I/O Ports as I have the data sheet for my card and I know the address and data ports for it. I think the traditional approach is to use method 01 above, but I am hoping to get around it using 02, or 03.
I'll keep trying using methods 2 and 3 and I'll keep you posted. Thanks
What does the following actually suggest:
What is the "processor address space" is that RAM? What does "relative to the base address" mean, is that Address+Offset?The BAR is written to by software to map the device regis-
ters into a window of processor address space. Once this mapping is
done, the device registers can be accessed relative to the base address.
