../kernel/Vsprintf.c
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#include <linux/config.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/hdreg.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/segment.h>
/*
* This code handles all hd-interrupts, and read/write requests to
* the hard-disk. It is relatively straigthforward (not obvious maybe,
* but interrupts never are), while still being efficient, and never
* disabling interrupts (except to overcome possible race-condition).
* The elevator block-seek algorithm doesn't need to disable interrupts
* due to clever programming.
*/
/* Max read/write errors/sector */
#define MAX_ERRORS 5
#define MAX_HD 2
#define NR_REQUEST 32
/*
* This struct defines the HD's and their types.
* Currently defined for CP3044's, ie a modified
* type 17.
*/
static struct hd_i_struct{
int head,sect,cyl,wpcom,lzone,ctl;
} hd_info[]= { HD_TYPE };
#define NR_HD ((sizeof (hd_info))/(sizeof (struct hd_i_struct)))
static struct hd_struct {
long start_sect;
long nr_sects;
} hd[5*MAX_HD]={{0,0},}; //一个硬盘可分5个区，共有2个硬盘
static struct hd_request {
int hd; /* -1 if no request */
int nsector;
int sector;
int head;
int cyl;
int cmd;
int errors;
struct buffer_head * bh;
struct hd_request * next;
} request[NR_REQUEST];
#define IN_ORDER(s1,s2) \
((s1)->hd<(s2)->hd || (s1)->hd==(s2)->hd && \
((s1)->cyl<(s2)->cyl || (s1)->cyl==(s2)->cyl && \
((s1)->head<(s2)->head || (s1)->head==(s2)->head && \
((s1)->sector<(s2)->sector))))
static struct hd_request * this_request = NULL;
static int sorting=0;
static void do_request(void);
static void reset_controller(void);
static void rw_abs_hd(int rw,unsigned int nr,unsigned int sec,unsigned int head,
unsigned int cyl,struct buffer_head * bh);
void hd_init(void);
#define port_read(port,buf,nr) \
//下面的内嵌汇编的意思是：
// movl port %edx
// movl buf %edi
// movl nr %ecx
// cld
// rep insw //从edx指定的port传送字到es：edi指定的buf中
__asm__("cld;rep;insw"::"d" (port),"D" (buf),"c" (nr):"cx","di")
#define port_write(port,buf,nr) \
__asm__("cld;rep;outsw"::"d" (port),"S" (buf),"c" (nr):"cx","si") //其中outsw是从ds：si指定的buf中传送字到edx指定的port
extern void hd_interrupt(void); //在system_call.S中定义
static struct task_struct * wait_for_request=NULL;
static inline void lock_buffer(struct buffer_head * bh)
{
if (bh->b_lock) //此缓冲区是否上锁
printk("hd.c: buffer multiply locked\n");
bh->b_lock=1;
}
static inline void unlock_buffer(struct buffer_head * bh)
{
if (!bh->b_lock)
printk("hd.c: free buffer being unlocked\n");
bh->b_lock=0;
wake_up(&bh->b_wait);
}
static inline void wait_on_buffer(struct buffer_head * bh)
{
cli();
while (bh->b_lock)
sleep_on(&bh->b_wait); //进入等待对列
sti();
}
void rw_hd(int rw, struct buffer_head * bh) //缓冲区和磁盘之间交换数据
{
unsigned int block,dev;
unsigned int sec,head,cyl;
block = bh->b_blocknr << 1; //默认1块=1024字节，二个扇区
dev = MINOR(bh->b_dev);
if (dev >= 5*NR_HD || block+2 > hd[dev].nr_sects) //是否超过了分区，此分区是否满了
return;
block += hd[dev].start_sect; //此分区的开始扇区+block，即在硬盘中定开始的位置
dev /= 5; //看看是哪个硬盘
__asm__("divl %4":"=a" (block),"=d" (sec):"0" (block),"1" (0),
"r" (hd_info[dev].sect)); //确定扇区号
__asm__("divl %4":"=a" (cyl),"=d" (head):"0" (block),"1" (0),
"r" (hd_info[dev].head)); //确定光头号
rw_abs_hd(rw,dev,sec+1,head,cyl,bh); //实际写盘函数
}
/* This may be used only once, enforced by 'static int callable' */
int sys_setup(void)
{
static int callable = 1;
int i,drive;
struct partition *p;
if (!callable)
return -1;
callable = 0;
for (drive=0 ; drive<NR_HD ; drive++) {
rw_abs_hd(READ,drive,1,0,0,(struct buffer_head *) start_buffer); //读取引导扇区512字节到start_buffer中
if (!start_buffer->b_uptodate) {
printk("Unable to read partition table of drive %d\n\r",
drive);
panic("");
}
if (start_buffer->b_data[510] != 0x55 || (unsigned char)
start_buffer->b_data[511] != 0xAA) { //分析引导扇区是否合法，合法应为55AA
printk("Bad partition table on drive %d\n\r",drive);
panic("");
}
p = 0x1BE + (void *)start_buffer->b_data; //指针指向分区信息的开始位置
for (i=1;i<5;i++,p++) { //保存分区信息
hd[i+5*drive].start_sect = p->start_sect;
hd[i+5*drive].nr_sects = p->nr_sects;
}
}
printk("Partition table%s ok.\n\r",(NR_HD>1)?"s":"");
mount_root(); //在super.c中定义
return (0);
}
/*
* This is the pointer to a routine to be executed at every hd-interrupt.
* Interesting way of doing things, but should be rather practical.
*/
void (*do_hd)(void) = NULL;
static int controller_ready(void)
{
int retries=1000;
while (--retries && (inb(HD_STATUS)&0xc0)!=0x40); //0x40是第六个位置1为驱动器准备好，0x1f7端口是读取硬盘状态
return (retries);
}
static int win_result(void)
{
int i=inb(HD_STATUS); //读取硬盘状态
if ((i & (BUSY_STAT | READY_STAT | WRERR_STAT | SEEK_STAT | ERR_STAT))
== (READY_STAT | SEEK_STAT))
return(0); /* ok */
if (i&1) i=inb(HD_ERROR); //0x1f1是硬盘错误寄存器，检查上一个命令是否出错
return (1);
}
static void hd_out(unsigned int drive,unsigned int nsect,unsigned int sect,
unsigned int head,unsigned int cyl,unsigned int cmd,
void (*intr_addr)(void))
{
register int port asm("dx");
if (drive>1 || head>15) //只支持1个硬盘和14个头
panic("Trying to write bad sector");
if (!controller_ready())
panic("HD controller not ready");
do_hd = intr_addr; //硬盘写或读操作指针
outb(_CTL,HD_CMD); //0x3f6是硬盘控制寄存器，置0为控制器为普通操作
port=HD_DATA; //0x1f0硬盘数据寄存器
outb_p(_WPCOM,++port); //0x1f1，写预补偿，在从磁柱300X4处开始写
outb_p(nsect,++port); //0x1f2是硬盘扇区记数寄存器，将要传送的扇区数放入该寄存器
outb_p(sect,++port); //0x1f3是硬盘扇区号寄存器，记录当前的扇区号
outb_p(cyl,++port); //0x1f4硬盘磁柱低寄存器，保存起始磁柱号的低8字节
outb_p(cyl>>8,++port); //0x1f5硬盘磁柱高寄存器
outb_p(0xA0|(drive<<4)|head,++port); //0x1f6硬盘驱动器和磁头寄存器，这里选择主盘（高4位为1010），低4位为磁头号
outb(cmd,++port); //0x1f7硬盘命令输出寄存器，主要向硬盘发出命令
}
static int drive_busy(void)
{
unsigned int i;
for (i = 0; i < 100000; i++) //循环，直到驱动器为READY_STAT或超时
if (READY_STAT == (inb(HD_STATUS) & (BUSY_STAT | READY_STAT)))
break;
i = inb(HD_STATUS); //再读硬盘状态
i &= BUSY_STAT | READY_STAT | SEEK_STAT;
if (i == READY_STAT | SEEK_STAT) //如果处于读状态或寻找状态，OK
return(0);
printk("HD controller times out\n\r");
return(1);
}
static void reset_controller(void)
{
int i;
outb(4,HD_CMD); //0x3f6是硬盘适配器控制寄存器，第二位置1为重启控制器
for(i = 0; i < 1000; i++) nop(); //等待一会儿
outb(0,HD_CMD); //使驱动器处于普通状态
for(i = 0; i < 10000 && drive_busy(); i++) /* nothing */;
if (drive_busy())
printk("HD-controller still busy\n\r");
if((i = inb(ERR_STAT)) != 1)
printk("HD-controller reset failed: %02x\n\r",i);
}
static void reset_hd(int nr)
{
reset_controller();
hd_out(nr,_SECT,_SECT,_HEAD-1,_CYL,WIN_SPECIFY,&do_request); //do_request是重新处理请求队列
}
void unexpected_hd_interrupt(void)
{
panic("Unexpected HD interrupt\n\r");
}
static void bad_rw_intr(void)
{
int i = this_request->hd;
if (this_request->errors++ >= MAX_ERRORS) { //如果错误超过有效的最大错误数，放弃这次请求
this_request->bh->b_uptodate = 0;
unlock_buffer(this_request->bh);
wake_up(&wait_for_request);
this_request->hd = -1;
this_request=this_request->next;
}
reset_hd(i);
}
static void read_intr(void)
{
if (win_result()) {
bad_rw_intr();
return;
}
port_read(HD_DATA,this_request->bh->b_data+
512*(this_request->nsector&1),256); //是从b_data指定位置读512字节
this_request->errors = 0;
if (--this_request->nsector) //如果还有要传的数据，直接返回，不从请求队列中删除该请求
return;
//以下6行代码是指数据传送完毕，就从请求队列中删除该请求
this_request->bh->b_uptodate = 1;
this_request->bh->b_dirt = 0;
wake_up(&wait_for_request);
unlock_buffer(this_request->bh);
this_request->hd = -1;
this_request=this_request->next;
do_request(); //处理其他请求
}
static void write_intr(void)
{
if (win_result()) {
bad_rw_intr(); //如果有错误，重启驱动器，再继续处理请求
return;
}
if (--this_request->nsector) {
port_write(HD_DATA,this_request->bh->b_data+512,256); //向硬盘数据寄存器写数据
return;
}
this_request->bh->b_uptodate = 1;
this_request->bh->b_dirt = 0;
wake_up(&wait_for_request);
unlock_buffer(this_request->bh);
this_request->hd = -1;
this_request=this_request->next;
do_request(); //处理下一个请求
}
static void do_request(void)
{
int i,r;
if (sorting)
return;
if (!this_request) {
do_hd=NULL;
return;
}
if (this_request->cmd == WIN_WRITE) {
hd_out(this_request->hd,this_request->nsector,this_request->
sector,this_request->head,this_request->cyl,
this_request->cmd,&write_intr);
for(i=0 ; i<3000 && !(r=inb_p(HD_STATUS)&DRQ_STAT) ; i++) //循环，直到控制器指示准备好
/* nothing */ ;
if (!r) { //如果超时驱动器仍未准备好，重设该驱动器
reset_hd(this_request->hd);
return;
}
port_write(HD_DATA,this_request->bh->b_data+
512*(this_request->nsector&1),256); //传送数据
} else if (this_request->cmd == WIN_READ) {
hd_out(this_request->hd,this_request->nsector,this_request->
sector,this_request->head,this_request->cyl,
this_request->cmd,&read_intr);
} else
panic("unknown hd-command");
}
/*
* add-request adds a request to the linked list.
* It sets the 'sorting'-variable when doing something
* that interrupts shouldn't touch.
*/
static void add_request(struct hd_request * req)
{
struct hd_request * tmp;
if (req->nsector != 2)
panic("nsector!=2 not implemented");
/*
* Not to mess up the linked lists, we never touch the two first
* entries (not this_request, as it is used by current interrups,
* and not this_request->next, as it can be assigned to this_request).
* This is not too high a price to pay for the ability of not
* disabling interrupts.
*/
sorting=1;
if (!(tmp=this_request))
this_request=req;
else {
if (!(tmp->next))
tmp->next=req;
else {
tmp=tmp->next;
for ( ; tmp->next ; tmp=tmp->next)
if ((IN_ORDER(tmp,req) ||
!IN_ORDER(tmp,tmp->next)) &&
IN_ORDER(req,tmp->next))
break;
req->next=tmp->next;
tmp->next=req;
}
}
sorting=0;
/*
* NOTE! As a result of sorting, the interrupts may have died down,
* as they aren't redone due to locking with sorting=1. They might
* also never have started, if this is the first request in the queue,
* so we restart them if necessary.
*/
if (!do_hd)
do_request();
}
void rw_abs_hd(int rw,unsigned int nr,unsigned int sec,unsigned int head,
unsigned int cyl,struct buffer_head * bh) //根据硬盘参数做磁盘读写
{
struct hd_request * req;
if (rw!=READ && rw!=WRITE)
panic("Bad hd command, must be R/W");
lock_buffer(bh);
repeat:
for (req=0+request ; req<NR_REQUEST+request ; req++)
if (req->hd<0) //hd=-1表示没有请求
break;
if (req==NR_REQUEST+request) { //不能超过最大的请求数
sleep_on(&wait_for_request);
goto repeat;
}
req->hd=nr;
req->nsector=2; //==1024字节
req->sector=sec;
req->head=head;
req->cyl=cyl;
req->cmd = ((rw==READ)?WIN_READ:WIN_WRITE);
req->bh=bh;
req->errors=0;
req->next=NULL;
add_request(req);
wait_on_buffer(bh); //进入等待
}
void hd_init(void)
{
int i;
for (i=0 ; i<NR_REQUEST ; i++) { //初始化请求队列
request[i].hd = -1;
request[i].next = NULL;
}
for (i=0 ; i<NR_HD ; i++) { //初始化硬盘分区
hd[i*5].start_sect = 0;
hd[i*5].nr_sects = hd_info[i].head*
hd_info[i].sect*hd_info[i].cyl;
}
set_trap_gate(0x2E,&hd_interrupt); //登记硬盘中断处理程序，中断号为0x2E
outb_p(inb_p(0x21)&0xfb,0x21); //开放IRQ2（中断控制器1）
outb(inb_p(0xA1)&0xbf,0xA1); //开放IRQ14，硬盘控制器
}
