📄 linux设备驱动程序学习（10）-时间、延迟及延缓操作 - linux设备驱动程序 - tekkaman ninja.htm
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time_before_eq<SPAN
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<P>用户空间的时间表述法（struct timeval 和 struct timespec
）与内核表述法的转换函数：</P>
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<P
style="MARGIN: 5px; LINE-HEIGHT: 150%"><CODE><SPAN
style="COLOR: rgb(0,0,0)"><SPAN
style="COLOR: rgb(0,0,204)">#</SPAN><SPAN
style="COLOR: rgb(255,0,0)">include</SPAN> <SPAN
style="COLOR: rgb(0,0,204)"><</SPAN>linux<SPAN
style="COLOR: rgb(0,0,204)">/</SPAN><SPAN
style="COLOR: rgb(255,0,0)">time</SPAN><SPAN
style="COLOR: rgb(0,0,204)">.</SPAN>h<SPAN
style="COLOR: rgb(0,0,204)">></SPAN> <SPAN
style="COLOR: rgb(255,153,0)">/* #include
<linux/jiffies.h> -->
\kernel\time.c*/</SPAN><BR><BR><SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timespec</SPAN>
<SPAN
style="COLOR: rgb(0,0,204)">{</SPAN><BR> <SPAN
style="COLOR: rgb(255,0,0)">time_t</SPAN> tv_sec<SPAN
style="COLOR: rgb(0,0,204)">;</SPAN> <SPAN
style="COLOR: rgb(255,153,0)">/* seconds
*/</SPAN><BR> <SPAN
style="COLOR: rgb(0,0,255)">long</SPAN> tv_nsec<SPAN
style="COLOR: rgb(0,0,204)">;</SPAN> <SPAN
style="COLOR: rgb(255,153,0)">/* nanoseconds
*/</SPAN><BR><SPAN
style="COLOR: rgb(0,0,204)">}</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN><BR><SPAN
style="COLOR: rgb(0,0,204)">#</SPAN><SPAN
style="COLOR: rgb(255,0,0)">endif</SPAN><BR><BR><SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timeval</SPAN> <SPAN
style="COLOR: rgb(0,0,204)">{</SPAN><BR> <SPAN
style="COLOR: rgb(255,0,0)">time_t</SPAN> tv_sec<SPAN
style="COLOR: rgb(0,0,204)">;</SPAN> <SPAN
style="COLOR: rgb(255,153,0)">/* seconds
*/</SPAN><BR> suseconds_t tv_usec<SPAN
style="COLOR: rgb(0,0,204)">;</SPAN> <SPAN
style="COLOR: rgb(255,153,0)">/* microseconds
*/</SPAN><BR><SPAN
style="COLOR: rgb(0,0,204)">}</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN><BR><BR><SPAN
style="COLOR: rgb(0,0,255)">unsigned</SPAN>
<SPAN style="COLOR: rgb(0,0,255)">long</SPAN>
timespec_to_jiffies<SPAN
style="COLOR: rgb(0,0,204)">(</SPAN><SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timespec</SPAN>
<SPAN
style="COLOR: rgb(0,0,204)">*</SPAN>value<SPAN
style="COLOR: rgb(0,0,204)">)</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN><BR><SPAN
style="COLOR: rgb(0,0,255)">void</SPAN>
jiffies_to_timespec<SPAN
style="COLOR: rgb(0,0,204)">(</SPAN><SPAN
style="COLOR: rgb(0,0,255)">unsigned</SPAN>
<SPAN style="COLOR: rgb(0,0,255)">long</SPAN>
jiffies<SPAN
style="COLOR: rgb(0,0,204)">,</SPAN> <SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timespec</SPAN>
<SPAN
style="COLOR: rgb(0,0,204)">*</SPAN>value<SPAN
style="COLOR: rgb(0,0,204)">)</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN><BR><SPAN
style="COLOR: rgb(0,0,255)">unsigned</SPAN>
<SPAN style="COLOR: rgb(0,0,255)">long</SPAN>
timeval_to_jiffies<SPAN
style="COLOR: rgb(0,0,204)">(</SPAN><SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timeval</SPAN> <SPAN
style="COLOR: rgb(0,0,204)">*</SPAN>value<SPAN
style="COLOR: rgb(0,0,204)">)</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN><BR><SPAN
style="COLOR: rgb(0,0,255)">void</SPAN>
jiffies_to_timeval<SPAN
style="COLOR: rgb(0,0,204)">(</SPAN><SPAN
style="COLOR: rgb(0,0,255)">unsigned</SPAN>
<SPAN style="COLOR: rgb(0,0,255)">long</SPAN>
jiffies<SPAN
style="COLOR: rgb(0,0,204)">,</SPAN> <SPAN
style="COLOR: rgb(0,0,255)">struct</SPAN> <SPAN
style="COLOR: rgb(255,0,0)">timeval</SPAN> <SPAN
style="COLOR: rgb(0,0,204)">*</SPAN>value<SPAN
style="COLOR: rgb(0,0,204)">)</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN></SPAN></CODE></P></TD></TR></TBODY></TABLE>
<P>访问jiffies_64 对于 32-位
处理器不是原子的，这意味着如果这个变量在你正在读取它们时被更新你可能读到错误的值。若需要访问jiffies_64，内核有一个特别的辅助函数，为你完成适当的锁定:
</P>
<P>
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<P
style="MARGIN: 5px; LINE-HEIGHT: 150%"><CODE><SPAN
style="COLOR: rgb(0,0,0)"><FONT face=新宋体><SPAN
style="COLOR: rgb(0,0,204)">#</SPAN><SPAN
style="COLOR: rgb(255,0,0)">include</SPAN> <SPAN
style="COLOR: rgb(0,0,204)"><</SPAN>linux<SPAN
style="COLOR: rgb(0,0,204)">/</SPAN>jiffies<SPAN
style="COLOR: rgb(0,0,204)">.</SPAN>h<SPAN
style="COLOR: rgb(0,0,204)">></SPAN> <BR>u64
get_jiffies_64<SPAN
style="COLOR: rgb(0,0,204)">(</SPAN><SPAN
style="COLOR: rgb(0,0,255)">void</SPAN><SPAN
style="COLOR: rgb(0,0,204)">)</SPAN><SPAN
style="COLOR: rgb(0,0,204)">;</SPAN></FONT></SPAN></CODE></P></TD></TR></TBODY></TABLE></P>
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