Author: kib Date: Sat Aug 12 08:51:19 2017 New Revision: 322422 URL: https://svnweb.freebsd.org/changeset/base/322422
Log: MFC r322077: Provide more detailed specification for major(), minor() and makedev(). Modified: stable/11/share/man/man3/makedev.3 Directory Properties: stable/11/ (props changed) Modified: stable/11/share/man/man3/makedev.3 ============================================================================== --- stable/11/share/man/man3/makedev.3 Fri Aug 11 23:12:28 2017 (r322421) +++ stable/11/share/man/man3/makedev.3 Sat Aug 12 08:51:19 2017 (r322422) @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd September 28, 2008 +.Dd August 3, 2017 .Dt MAKEDEV 3 .Os .Sh NAME @@ -43,7 +43,7 @@ .Sh DESCRIPTION The .Fn makedev -macro allows a unique device number to be generated based on its +macro returns a device number created from the provided .Fa major and .Fa minor @@ -52,13 +52,26 @@ The .Fn major and .Fn minor -macros can be used to obtain the original numbers from the device number +macros return the original numbers from the device number .Fa dev . +In other words, for a value +.Va dev +of the type +.Vt dev_t , +and values +.Va ma , mi +of the type +.Vt int , +the assertions +.Dl dev == makedev(major(dev), minor(dev)) +.Dl ma == major(makedev(ma, mi)) +.Dl mi == minor(makedev(ma, mi)) +are valid. .Pp In previous implementations of .Fx all block and character devices were uniquely identified by a pair of -major and minor numbers. +stable major and minor numbers. The major number referred to a certain device class (e.g. disks, TTYs) while the minor number identified an instance within the device class. Later versions of @@ -66,7 +79,8 @@ Later versions of automatically generate a unique device number for each character device visible in .Pa /dev/ . -These numbers are not divided in device classes. +These numbers are not divided in device classes and are not guaranteed +to be stable upon reboot or driver reload. .Pp On .Fx @@ -78,11 +92,9 @@ conventional way. .Sh RETURN VALUES The .Fn major -macro returns a device major number that has a value between 0 and 255. -The +and .Fn minor -macro returns a device minor number whose value can span the complete -range of an +macros return numbers whose value can span the complete range of an .Vt int . .Sh SEE ALSO .Xr mknod 2 , _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
