>Hi, >I am trying to understand PCI unsuccessfully. >Let's say i have 4 GB of RAM and x86 32bit. >Now, i have 1 PCI card with a device on it. It has 4gb worth of registers. I.e. memory. So, it sits on bus:0, device:1 function:2. >1) If i wish to address just two words (to be set to 0xffee) (32 bits) >register on address 0xe0000000. What will be the hardware steps to take? >My guess work (and please CMIIW): The address bus register on the cpu is >set >to 0xe0000000, the CPU data bus is switched to PCI bus 0 and somewhere on the >bus 0 controller we set a register to 0x110 to represent device:1 >function:2. >The CPU then writes to it's data bus 0xffee and we are done. >Also, i would appreciate to have the actual commands in linux to do the above. >2) The PCI device now wants it's memory to be i/o memory mapped to ram (probably at boottime) so i can write *my_memmaped_pointer=0xffee; What are the steps to do that in linux? >Btw, i am in serious doubt that there are devices on a PC x86 that allows a >PCI to directly connect it's data bus and address bus to the RAM address and >data bus like handheld computers does etc... instead of working like a port on ISA (i.e. a separate bus). First have a look at the /proc/pci. It gives good amount of information on PCI devices connected. Once you find the device you are looking for,. u can get the Pci_dev reference with vendor id and device id. pci_dev = pci_find_device(Vendor, devid, NULL/*First reference*/); PCI Device can support 6 IO regions, and the address of the these regions will be stored in Configuration space of the pci device, Exact location where these address will be stored is referred as BAR(Base address register), there are 6 BARs ranged from 0-5. Start_add = Pci_resource_start(pci_dev, bar_no); End_addr = pci_resource_end(pci_dev, bar_no); Now with these you can make a request for ioremap. ioremap(start, size /*end - start +1*/); now you can use read and write functions to access the pci memory region... CMIIW... -Vamsi -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
