74.html

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<a name='L278'>    <font color='red'>}</font>
<a name='L279'><font color='red'>}</font>
<a name='L280'>
<a name='L281'><i><font color='green'>/*</font></i>
<a name='L282'><i><font color='green'> * OK, here are some floppy things that shouldn't be in the kernel</font></i>
<a name='L283'><i><font color='green'> * proper. They are here because the floppy needs a timer, and this</font></i>
<a name='L284'><i><font color='green'> * was the easiest way of doing it.</font></i>
<a name='L285'><i><font color='green'> */</font></i>
<a name='L286'><i><font color='green'>/*</font></i>
<a name='L287'><i><font color='green'> * 好了，从这里开始是一些有关软盘的子程序，本不应该放在内核的主要部分中的。将它们放在这里</font></i>
<a name='L288'><i><font color='green'> * 是因为软驱需要一个时钟，而放在这里是最方便的办法。</font></i>
<a name='L289'><i><font color='green'> */</font></i>
<a name='L290'><b>static</b> <b>struct</b> task_struct *wait_motor[4] = <font color='red'>{</font> <a href='../D/261.html' title='Multiple defined in 12 places.'>NULL</a>, <a href='../D/261.html' title='Multiple defined in 12 places.'>NULL</a>, <a href='../D/261.html' title='Multiple defined in 12 places.'>NULL</a>, <a href='../D/261.html' title='Multiple defined in 12 places.'>NULL</a> <font color='red'>}</font>;
<a name='L291'><b>static</b> <b>int</b> mon_timer[4] = <font color='red'>{</font> 0, 0, 0, 0 <font color='red'>}</font>;
<a name='L292'><b>static</b> <b>int</b> moff_timer[4] = <font color='red'>{</font> 0, 0, 0, 0 <font color='red'>}</font>;
<a name='L293'><b>unsigned</b> <b>char</b> current_DOR = 0x0C;       <i><font color='green'>// 数字输出寄存器(初值：允许DMA 和请求中断、启动FDC)。</font></i>
<a name='L294'>
<a name='L295'><i><font color='green'>// 指定软盘到正常运转状态所需延迟滴答数（时间）。</font></i>
<a name='L296'><i><font color='green'>// nr -- 软驱号(0-3)，返回值为滴答数。</font></i>
<a name='L297'><b>int</b>
<a name='L298'><a href='../R/701.html' title='Multiple refered from 3 places.'>ticks_to_floppy_on</a> (<b>unsigned</b> <b>int</b> nr)
<a name='L299'><font color='red'>{</font>
<a name='L300'>  <b>extern</b> <b>unsigned</b> <b>char</b> selected;        <i><font color='green'>// 当前选中的软盘号(kernel/blk_drv/floppy.c,122)。</font></i>
<a name='L301'>  <b>unsigned</b> <b>char</b> mask = 0x10 &lt;&lt; nr;      <i><font color='green'>// 所选软驱对应数字输出寄存器中启动马达比特位。</font></i>
<a name='L302'>
<a name='L303'>  <b>if</b> (nr &gt; 3)
<a name='L304'>    <a href='../S/72.html#L24' title='Defined at 24 in kernel/panic.c.'>panic</a> ("floppy_on: nr&gt;3");  <i><font color='green'>// 最多4 个软驱。</font></i>
<a name='L305'>  moff_timer[nr] = 10000;       <i><font color='green'>/* 100 s = very big :-) */</font></i>
<a name='L306'>  <a href='../S/25.html#L15' title='Defined at 15 in include/asm/system.h.'>cli</a> ();                       <i><font color='green'>/* use floppy_off to turn it off */</font></i>
<a name='L307'>  mask |= current_DOR;
<a name='L308'>  <i><font color='green'>// 如果不是当前软驱，则首先复位其它软驱的选择位，然后置对应软驱选择位。</font></i>
<a name='L309'>  <b>if</b> (!selected)
<a name='L310'>    <font color='red'>{</font>
<a name='L311'>      mask &amp;= 0xFC;
<a name='L312'>      mask |= nr;
<a name='L313'>    <font color='red'>}</font>
<a name='L314'>  <i><font color='green'>// 如果数字输出寄存器的当前值与要求的值不同，则向FDC 数字输出端口输出新值(mask)。并且如果</font></i>
<a name='L315'>  <i><font color='green'>// 要求启动的马达还没有启动，则置相应软驱的马达启动定时器值(HZ/2 = 0.5 秒或50 个滴答)。</font></i>
<a name='L316'>  <i><font color='green'>// 此后更新当前数字输出寄存器值current_DOR。</font></i>
<a name='L317'>  <b>if</b> (mask != current_DOR)
<a name='L318'>    <font color='red'>{</font>
<a name='L319'>      <a href='../S/22.html#L3' title='Defined at 3 in include/asm/io.h.'>outb</a> (mask, FD_DOR);
<a name='L320'>      <b>if</b> ((mask ^ current_DOR) &amp; 0xf0)
<a name='L321'>        mon_timer[nr] = <a href='../S/36.html#L5' title='Defined at 5 in include/linux/sched.h.'>HZ</a> / 2;
<a name='L322'>      <b>else</b> <b>if</b> (mon_timer[nr] &lt; 2)
<a name='L323'>        mon_timer[nr] = 2;
<a name='L324'>      current_DOR = mask;
<a name='L325'>    <font color='red'>}</font>
<a name='L326'>  <a href='../S/25.html#L14' title='Defined at 14 in include/asm/system.h.'>sti</a> ();
<a name='L327'>  <b>return</b> mon_timer[nr];
<a name='L328'><font color='red'>}</font>
<a name='L329'>
<a name='L330'><i><font color='green'>// 等待指定软驱马达启动所需时间。</font></i>
<a name='L331'><b>void</b>
<a name='L332'><a href='../R/460.html' title='Multiple refered from 3 places.'>floppy_on</a> (<b>unsigned</b> <b>int</b> nr)
<a name='L333'><font color='red'>{</font>
<a name='L334'>  <a href='../S/25.html#L15' title='Defined at 15 in include/asm/system.h.'>cli</a> ();                       <i><font color='green'>// 关中断。</font></i>
<a name='L335'>  <b>while</b> (<a href='../S/74.html#L298' title='Defined at 298 in kernel/sched.c.'>ticks_to_floppy_on</a> (nr))       <i><font color='green'>// 如果马达启动定时还没到，就一直把当前进程置</font></i>
<a name='L336'>    <a href='../S/74.html#L219' title='Defined at 219 in kernel/sched.c.'>sleep_on</a> (nr + wait_motor); <i><font color='green'>// 为不可中断睡眠状态并放入等待马达运行的队列中。</font></i>
<a name='L337'>  <a href='../S/25.html#L14' title='Defined at 14 in include/asm/system.h.'>sti</a> ();                       <i><font color='green'>// 开中断。</font></i>
<a name='L338'><font color='red'>}</font>
<a name='L339'>
<a name='L340'><i><font color='green'>// 置关闭相应软驱马达停转定时器（3 秒）。</font></i>
<a name='L341'><b>void</b>
<a name='L342'><a href='../R/459.html' title='Multiple refered from 4 places.'>floppy_off</a> (<b>unsigned</b> <b>int</b> nr)
<a name='L343'><font color='red'>{</font>
<a name='L344'>  moff_timer[nr] = 3 * <a href='../S/36.html#L5' title='Defined at 5 in include/linux/sched.h.'>HZ</a>;
<a name='L345'><font color='red'>}</font>
<a name='L346'>
<a name='L347'><i><font color='green'>// 软盘定时处理子程序。更新马达启动定时值和马达关闭停转计时值。该子程序是在时钟定时</font></i>
<a name='L348'><i><font color='green'>// 中断中被调用，因此每一个滴答(10ms)被调用一次，更新马达开启或停转定时器的值。如果某</font></i>
<a name='L349'><i><font color='green'>// 一个马达停转定时到，则将数字输出寄存器马达启动位复位。</font></i>
<a name='L350'><b>void</b>
<a name='L351'><a href='../S/74.html#L471' title='Refered from 471 in kernel/sched.c.'>do_floppy_timer</a> (<b>void</b>)
<a name='L352'><font color='red'>{</font>
<a name='L353'>  <b>int</b> <a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>;
<a name='L354'>  <b>unsigned</b> <b>char</b> mask = 0x10;
<a name='L355'>
<a name='L356'>  <b>for</b> (<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a> = 0; <a href='../D/839.html' title='Multiple defined in 4 places.'>i</a> &lt; 4; <a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>++, mask &lt;&lt;= 1)
<a name='L357'>    <font color='red'>{</font>
<a name='L358'>      <b>if</b> (!(mask &amp; current_DOR))        <i><font color='green'>// 如果不是DOR 指定的马达则跳过。</font></i>
<a name='L359'>        <b>continue</b>;
<a name='L360'>      <b>if</b> (mon_timer[<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>])
<a name='L361'>        <font color='red'>{</font>
<a name='L362'>          <b>if</b> (!--mon_timer[<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>])
<a name='L363'>            <a href='../S/74.html#L272' title='Defined at 272 in kernel/sched.c.'>wake_up</a> (<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a> + wait_motor);   <i><font color='green'>// 如果马达启动定时到则唤醒进程。</font></i>
<a name='L364'>        <font color='red'>}</font>
<a name='L365'>      <b>else</b> <b>if</b> (!moff_timer[<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>])
<a name='L366'>        <font color='red'>{</font>                       <i><font color='green'>// 如果马达停转定时到则</font></i>
<a name='L367'>          current_DOR &amp;= ~mask; <i><font color='green'>// 复位相应马达启动位，并</font></i>
<a name='L368'>          <a href='../S/22.html#L3' title='Defined at 3 in include/asm/io.h.'>outb</a> (current_DOR, FD_DOR);   <i><font color='green'>// 更新数字输出寄存器。</font></i>
<a name='L369'>        <font color='red'>}</font>
<a name='L370'>      <b>else</b>
<a name='L371'>        moff_timer[<a href='../D/839.html' title='Multiple defined in 4 places.'>i</a>]--;        <i><font color='green'>// 马达停转计时递减。</font></i>
<a name='L372'>    <font color='red'>}</font>
<a name='L373'><font color='red'>}</font>
<a name='L374'>
<a name='L375'><font color='darkred'>#define</font> <a href='../R/269.html' title='Multiple refered from 3 places.'>TIME_REQUESTS</a> 64        <i><font color='green'>// 最多可有64 个定时器链表（64 个任务）。</font></i>
<a name='L376'>
<a name='L377'><i><font color='green'>// 定时器链表结构和定时器数组。</font></i>
<a name='L378'><b>static</b> <b>struct</b> timer_list
<a name='L379'><font color='red'>{</font>
<a name='L380'>  <b>long</b> jiffies;                 <i><font color='green'>// 定时滴答数。</font></i>
<a name='L381'>  <b>void</b> (*fn) ();                <i><font color='green'>// 定时处理程序。</font></i>
<a name='L382'>  <b>struct</b> timer_list *next;      <i><font color='green'>// 下一个定时器。</font></i>
<a name='L383'><font color='red'>}</font>
<a name='L384'>timer_list[<a href='../S/74.html#L375' title='Defined at 375 in kernel/sched.c.'>TIME_REQUESTS</a>], *next_timer = <a href='../D/261.html' title='Multiple defined in 12 places.'>NULL</a>;
<a name='L385'>
<a name='L386'><i><font color='green'>// 添加定时器。输入参数为指定的定时值(滴答数)和相应的处理程序指针。</font></i>
<a name='L387'><i><font color='green'>// jiffies – 以10 毫秒计的滴答数；*fn()- 定时时间到时执行的函数。</font></i>
<a name='L388'><b>void</b>
<a name='L389'><a href='../R/383.html' title='Multiple refered from 3 places.'>add_timer</a> (<b>long</b> jiffies, <b>void</b> (*fn) (<b>void</b>))
<a name='L390'><font color='red'>{</font>
<a name='L391'>  <b>struct</b> timer_list *p;
<a name='L392'>
<a name='L393'>  <i><font color='green'>// 如果定时处理程序指针为空，则退出。</font></i>
<a name='L394'>  <b>if</b> (!fn)
<a name='L395'>    <b>return</b>;
<a name='L396'>  <a href='../S/25.html#L15' title='Defined at 15 in include/asm/system.h.'>cli</a> ();
<a name='L397'>  <i><font color='green'>// 如果定时值&lt;=0，则立刻调用其处理程序。并且该定时器不加入链表中。</font></i>
<a name='L398'>  <b>if</b> (jiffies &lt;= 0)
<a name='L399'>    (fn) ();
<a name='L400'>  <b>else</b>
<a name='L401'>    <font color='red'>{</font>
<a name='L402'>      <i><font color='green'>// 从定时器数组中，找一个空闲项。</font></i>
<a name='L403'>      <b>for</b> (p = timer_list; p &lt; timer_list + <a href='../S/74.html#L375' title='Defined at 375 in kernel/sched.c.'>TIME_REQUESTS</a>; p++)
<a name='L404'>        <b>if</b> (!p-&gt;fn)
<a name='L405'>          <b>break</b>;
<a name='L406'>      <i><font color='green'>// 如果已经用完了定时器数组，则系统崩溃?。</font></i>
<a name='L407'>      <b>if</b> (p &gt;= timer_list + <a href='../S/74.html#L375' title='Defined at 375 in kernel/sched.c.'>TIME_REQUESTS</a>)
<a name='L408'>        <a href='../S/72.html#L24' title='Defined at 24 in kernel/panic.c.'>panic</a> ("No more time requests free");
<a name='L409'>      <i><font color='green'>// 向定时器数据结构填入相应信息。并链入链表头</font></i>
<a name='L410'>      p-&gt;fn = fn;
<a name='L411'>      p-&gt;jiffies = jiffies;
<a name='L412'>      p-&gt;next = next_timer;
<a name='L413'>      next_timer = p;
<a name='L414'>      <i><font color='green'>// 链表项按定时值从小到大排序。在排序时减去排在前面需要的滴答数，这样在处理定时器时只要</font></i>
<a name='L415'>      <i><font color='green'>// 查看链表头的第一项的定时是否到期即可。[[?? 这段程序好象没有考虑周全。如果新插入的定时</font></i>
<a name='L416'>      <i><font color='green'>// 器值 &lt; 原来头一个定时器值时，也应该将所有后面的定时值均减去新的第1 个的定时值。]]</font></i>
<a name='L417'>      <b>while</b> (p-&gt;next &amp;&amp; p-&gt;next-&gt;jiffies &lt; p-&gt;jiffies)
<a name='L418'>        <font color='red'>{</font>
<a name='L419'>          p-&gt;jiffies -= p-&gt;next-&gt;jiffies;
<a name='L420'>          fn = p-&gt;fn;
<a name='L421'>          p-&gt;fn = p-&gt;next-&gt;fn;
<a name='L422'>          p-&gt;next-&gt;fn = fn;
<a name='L423'>          jiffies = p-&gt;jiffies;
<a name='L424'>          p-&gt;jiffies = p-&gt;next-&gt;jiffies;
<a name='L425'>          p-&gt;next-&gt;jiffies = jiffies;
<a name='L426'>          p = p-&gt;next;
<a name='L427'>        <font color='red'>}</font>
<a name='L428'>    <font color='red'>}</font>
<a name='L429'>  <a href='../S/25.html#L14' title='Defined at 14 in include/asm/system.h.'>sti</a> ();
<a name='L430'><font color='red'>}</font>
<a name='L431'>
<a name='L432'><i><font color='green'>//// 时钟中断C 函数处理程序，在kernel/system_call.s 中的_timer_interrupt（176 行）被调用。</font></i>
<a name='L433'><i><font color='green'>// 参数cpl 是当前特权级0 或3，0 表示内核代码在执行。</font></i>
<a name='L434'><i><font color='green'>// 对于一个进程由于执行时间片用完时，则进行任务切换。并执行一个计时更新工作。</font></i>
<a name='L435'><b>void</b>
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