skull code of rubini's book -- http://www.xml.com/ldd/chapter/book/ch08.html#t4 -- usbsection Probing for ISA Memory (listed at end of this mail) -- probe all ISA memory range. It can reach: 1- Memory allocated. 2- RAM memory. 3- empty memory. (or 4-ROM yet, but i think we can ignore this fact here) But i think one possibility is missing: if is there a ISA hardware whose driver wasn't loaded yet? Since the driver wasn't uploaded yet, code does not reach a Memory allocated region. I think such region is nor a RAM region neither an empty region (because there is a hardware)... Where am I wrong? When code reach such region, what does it think is that region? RAM or empty memory? TIA. -Riba Code Listing: unsigned char oldval, newval; /* values read from memory */ unsigned long flags; /* used to hold system flags */ unsigned long add, i; void *base; /* Use ioremap to get a handle on our region */ base = ioremap(ISA_REGION_BEGIN, ISA_REGION_END - ISA_REGION_BEGIN); base -= ISA_REGION_BEGIN; /* Do the offset once */ /* probe all the memory hole in 2-KB steps */ for (add = ISA_REGION_BEGIN; add < ISA_REGION_END; add += STEP) { /* * Check for an already allocated region. */ if (check_mem_region (add, 2048)) { printk(KERN_INFO "%lx: Allocated\n", add); continue; } /* * Read and write the beginning of the region and see what happens. */ save_flags(flags); cli(); oldval = readb (base + add); /* Read a byte */ writeb (oldval^0xff, base + add); mb(); newval = readb (base + add); writeb (oldval, base + add); restore_flags(flags); if ((oldval^newval) == 0xff) { /* we reread our change: it's RAM */ printk(KERN_INFO "%lx: RAM\n", add); continue; } if ((oldval^newval) != 0) { /* random bits changed: it's empty */ printk(KERN_INFO "%lx: empty\n", add); continue; } -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
