1999-01-08 13:05:24

by David Grothe

[permalink] [raw]
Subject: poll.h


I am surveying all the poll.h files that I can find to see if there is a
of values for the poll bits that will be mutually compatible. I am
focusing on the I386 values for Linux.

Linux STREAMS (LiS) has its own poll.h that was created before Linux had
a poll.h, so I have included its values as well. At the present moment
the LiS poll.h includes linux/poll.h for kernel versions 2.1 and 2.2,
thus deferring to whatever is defined for the kernel. I have no problem
with changing the LiS values.

However, the kernel file asm-i386/poll.h contains the following comment
and definitions for some of the bits:

/* The rest seem to be more-or-less nonstandard. Check them! */
#define POLLRDNORM 0x0040
#define POLLRDBAND 0x0080
#define POLLWRNORM 0x0100
#define POLLWRBAND 0x0200
#define POLLMSG 0x0400

Well, I just checked them. The results are summarized in the following

In the table, "N/S" means "Not Specified" by that system.

Conflicts are noted with a "*". Where conflicts occur with other
Unix systems, such as Solaris or UnixWare 7, I marked only the Linux/LiS
files, accepting the Unix values as authoritative.

UnxWre7 Linux
I86 Sparc 2.2.0pre4
Variable LiS Solaris Solaris SCO I386
POLLIN 0x0001 0x0001 0x0001 0x0001 0x0001
POLLPRI 0x0002 0x0002 0x0002 0x0002 0x0002
POLLOUT 0x0004 0x0004 0x0004 0x0004 0x0004
POLLERR 0x0008 0x0008 0x0008 0x0008 0x0008
POLLWRNORM 0x0004 0x0004 0x0004 0x0004 0x0100*
POLLHUP 0x0010 0x0010 0x0010 0x0010 0x0010
POLLNVAL 0x0020 0x0020 0x0020 0x0020 0x0020
POLLRDNORM 0x0040 0x0040 0x0040 0x0040 0x0040
POLLNORM 0x0040 0x0040 0x0040 N/S N/S
POLLRDBAND 0x0080 0x0080 0x0080 0x0080 0x0080
POLLWRBAND 0x0100 0x0100 0x0100 0x0100 0x0200*
POLLMSG 0x0200* N/S N/S N/S 0x0400*

Note that the values that the comment wants to be checked are in
conflict with all the Unix versions surveyed. It would make sense to
change POLLWRNORM to 0x0004 and POLLWRBAND to 0x0100. The value for
POLLMSG could be left at 0x0400 or changed to 0x0200 to use the "next
available value".

Notice also that the Unix definitions explicitly set POLLWRNORM to the
same value as POLLOUT. This appears to be intentional as they define
these values in the following way:


I notice that quite a few drivers use POLLWRNORM. This could pose a

What do you all think of the idea of changing these values at this point
in time before 2.2 gets set in concrete?

Thanks for your time,

-- Dave