你怎么能刷新使用文件描述符写？ [英] How can you flush a write using a file descriptor?

问题描述

原来开（）与fopen（）函数从在Linux 2.6.14内核在手腕上的越野车I2C驱动茎的这整个误解。向后移植工作有点殴打司机解决了，我想在这里解决问题的根本原因。

It turns out this whole misunderstanding of the open() versus fopen() stems from a buggy I2C driver in the Linux 2.6.14 kernel on an ARM. Backporting a working bit bashed driver solved the root cause of the problem I was trying to address here.

我想弄清楚的一个问题，在Linux操作系统（I2C）串行设备驱动程序。看来，通过增加写入之间定时OS暂停（睡），并读取工作的事情在设备上......（多）更好。

I'm trying to figure out an issue with a serial device driver in Linux (I2C). It appears that by adding timed OS pauses (sleeps) between writes and reads on the device things work ... (much) better.

旁白：的 I2C的本质是由主机读取或写入每个字节由设备承认在电线​​上（从）的另一端 - 改进的东西停顿鼓励我想到司机作为异步工作 - 这是我不能用公交车是如何工作的协调。安美居... 的

我要么喜欢为刷新写可以肯定（而不是使用固定的工期暂停）， 或的不知何故测试该读/写交易都有完成在多线程友好的方式即可。

I'd either like to flush the write to be sure (rather than using fixed duration pause), or somehow test that the write/read transaction has completed in an multi-threaded friendly way.

使用麻烦的 fflush（FD）; 是，它需要的fd是流指针（不是文件描述符）即

The trouble with using fflush(fd); is that it requires 'fd' to be stream pointer (not a file descriptor) i.e.

FILE * fd = fopen("filename","r+");
... // do read and writes
fflush(fd);

我的问题是我需要使用的ioctl（），它不使用流指针。即。

My problem is that I require the use of the ioctl(), which doesn't use a stream pointer. i.e.

int fd = open("filename",O_RDWR);
ioctl(fd,...);

建议？

推荐答案

您有两种选择：

1. 使用的fileno（）来获得与 STDIO 流指针有关的文件描述符

1. Use fileno() to obtain the file descriptor associated with the stdio stream pointer

不要使用＆LT;＆stdio.h中GT; 可言，这样你就不需要担心冲洗要么 - 所有的写操作会去该装置立即和字符设备的的write（）通话甚至不会返回，直到下层IO已完成（理论上）。

Don't use <stdio.h> at all, that way you don't need to worry about flush either - all writes will go to the device immediately, and for character devices the write() call won't even return until the lower-level IO has completed (in theory).

有关设备级的IO我会说这是pretty不寻常的使用 STDIO 。我强烈建议使用较低级别的的open（），阅读（）和写（）函数，而不是（根据你以后的回复）：

For device-level IO I'd say it's pretty unusual to use stdio. I'd strongly recommend using the lower-level open(), read() and write() functions instead (based on your later reply):

int fd = open("/dev/i2c", O_RDWR);
ioctl(fd, IOCTL_COMMAND, args);
write(fd, buf, length);

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