Read the following article on PIC devices: http://www.tldp.org/LDP/tlk/dd/pci.html It tells something about, how PCI devices are given address by BIOS at startup. It's the BIOS which actually allocate the addresses to PCI device ports and then kernel can read the configuration registers of PIC device to know the status and address space of device. Every PCI device have the range of ports address which are valid for that device these are set into configuration memory of PCI and if PIC sees any address on system address bus between these range limits, it knows that control command (on control bus) or data (on data bus) is ment for it. Gaurav. -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of Om Sent: Tuesday, September 21, 2004 11:42 PM To: kernelnewbies Subject: PCI memory cycles and accessing memory. hi all, We are programming a non transparent bridge (plx6540cb) for linux (2.4.22) on opteron. We programmed the BAR1 with an address (0x8000_0000). Set up the downstream access registers and addresses (all non prefetchable memory). Now we would like to access the memory space on the secondary side of the bridge. My questions are not specific to the above mentioned bridge. They are more basic. ;-) * How does the Linux kernel know that 0x8000_0000 is allocated for this particular bridge? How exactly an access to 0x8000_0000 gets converted to memory cycles on PCI? What is the sequence of code functions.. etc. (just file/functions will suffice ) After assigning this address, we do request_mem_region() and ioremap(). The /proc/iomem shows this region as allocated to our driver as well. But I am clueless about the convertion of this address to PCI memory cycles. * What should be the functions that we should use to access the memory mapped regions? Is it inb() outb() readw() writew()..etc? Or access the memory by * operator would suffice? Regards, Om. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
