Messages in this thread |  | | | From | Kay Sievers <> | | Date | Fri, 6 Aug 2010 00:39:54 +0200 | | Subject | Re: [PATCH] [RFC] notify userspace about time changes |
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On Fri, Aug 6, 2010 at 00:34, H. Peter Anvin <hpa@zytor.com> wrote: > On 08/05/2010 03:22 PM, Kay Sievers wrote: >> >> I think that's really awkward interface, to pass file descriptor >> numbers around and write them to magic sysfs files. >> >> I would very much prefer a file that contains the current time, and >> wakes up possible users with a POLL_ERR on changes caused by some >> other process. That works very well for things like /proc/mounts, is >> easy to get, and does not need a full page of weird instructions to >> get stuff done. :) >> > > Okay, what's wrong with having a file descriptor that gets *written to* > on a notification?
Because it needs documentation, and is just not needed for such a simple thing, I think. Why would you want to write a fd number to a magic file, which can be your fd right away, even passing you the data on read().
> Why POLL_ERR?
Because normal files can not be poll()ed, and it's not that new data has arrived, it just tells you to rewind and read it again. It's commonly used: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5addc5dd8836aa061f6efc4a0d9ba6323726297a
Kay
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