O_CAREFUL flag to disable open() side effects

From: H. Peter Anvin
Date: Thu Jul 27 2006 - 13:32:03 EST

Alan Cox wrote:
Ar Iau, 2006-07-27 am 20:05 +0300, ysgrifennodd Pekka J Enberg:
Sure. Though I wonder if sys_frevoke is enough for us and we can drop sys_revoke completely.

Alas not. Some Unix devices have side effects when you open() them.

Dumb thought: would it make sense to add an O_CAREFUL flag to open(), to disable side effects? It seems that a number of devices have this issue and one have to jump through weird hoops to configure them. Obviously, a file descriptor obtained with O_CAREFUL may not be fully functional, at the device driver's option.

For a conventional file, directory, or block device O_CAREFUL is a no-op. For ttys it would typically behave similar to O_NONBLOCK followed immediately by a fcntl to clear the nonblock flag.

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