arch/x86/kernel/resource.c

   1 #include <linux/ioport.h>
   2 #include <asm/e820/api.h>
   3
   4 static void resource_clip(struct resource *res, resource_size_t start,
   5                           resource_size_t end)
   6 {
   7         resource_size_t low = 0, high = 0;
   8
   9         if (res->end < start || res->start > end)
  10                 return;         /* no conflict */
  11
  12         if (res->start < start)
  13                 low = start - res->start;
  14
  15         if (res->end > end)
  16                 high = res->end - end;
  17
  18         /* Keep the area above or below the conflict, whichever is larger */
  19         if (low > high)
  20                 res->end = start - 1;
  21         else
  22                 res->start = end + 1;
  23 }
  24
  25 static void remove_e820_regions(struct resource *avail)
  26 {
  27         int i;
  28         struct e820_entry *entry;
  29
  30         for (i = 0; i < e820_table->nr_entries; i++) {
  31                 entry = &e820_table->entries[i];
  32
  33                 resource_clip(avail, entry->addr,
  34                               entry->addr + entry->size - 1);
  35         }
  36 }
  37
  38 void arch_remove_reservations(struct resource *avail)
  39 {
  40         /*
  41          * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
  42          * the low 1MB unconditionally, as this area is needed for some ISA
  43          * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
  44          */
  45         if (avail->flags & IORESOURCE_MEM) {
  46                 resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
  47
  48                 remove_e820_regions(avail);
  49         }
  50 }