arch/mips/lib/tags.c

   1 /*
   2  *  linux/arch/mips/lib/tags.c
   3  *
   4  *  Copyright (C) 1996  Stoned Elipot
   5  */
   6 #include <linux/stddef.h>
   7 #include <linux/kernel.h>
   8 #include <linux/string.h>
   9 #include <asm/addrspace.h>
  10 #include <asm/bootinfo.h>
  11
  12 /*
  13  * Parse the tags present in upper memory to find out
  14  * a pecular one.
  15  *
  16  * Parameter: type - tag type to find
  17  *
  18  * returns  : NULL  - failure
  19  *            !NULL - pointer on the tag structure found
  20  */
  21 tag *
  22 bi_TagFind(enum bi_tag type)
  23 {
  24         tag* t = (tag*)(mips_memory_upper - sizeof(tag));
  25
  26         while((t->tag != tag_dummy) && (t->tag != type))
  27                 t = (tag*)(NEXTTAGPTR(t));
  28
  29         if (t->tag == tag_dummy)                /* tag not found */
  30                 return (tag*)NULL;
  31
  32         return t;
  33 }
  34
  35 /*
  36  * Snarf from the tag list in memory end some tags needed
  37  * before the kernel reachs setup_arch()
  38  *
  39  * add yours here if you want to, but *beware*: the kernel var
  40  * that will hold the values you want to snarf have to be
  41  * in .data section of the kernel, so initialized in to whatever
  42  * value in the kernel's sources.
  43  */
  44 void bi_EarlySnarf(void)
  45 {
  46         tag* atag;
  47
  48         /* for wire_mappings() */
  49         atag = bi_TagFind(tag_machgroup);
  50         if (atag)
  51                 memcpy(&mips_machgroup, TAGVALPTR(atag), atag->size);
  52         else {
  53                 /* useless for boxes without text video mode but....*/
  54                 panic("machine group not specified by bootloader");
  55         }
  56
  57         atag = bi_TagFind(tag_machtype);
  58         if (atag)
  59                 memcpy(&mips_machtype, TAGVALPTR(atag), atag->size);
  60         else {
  61                 /* useless for boxes without text video mode but....*/
  62                 panic("machine type not specified by bootloader");
  63         }
  64
  65         /* for tlbflush() */
  66         atag = bi_TagFind(tag_tlb_entries);
  67         if (atag)
  68                 memcpy(&mips_tlb_entries, TAGVALPTR(atag), atag->size);
  69         else {
  70                 /* useless for boxes without text video mode but....*/
  71                 panic("number of TLB entries not specified by bootloader");
  72         }
  73
  74         return;
  75 }