Date: Sat, 10 Jan 2009 16:10:42 -0800 From: perryh@pluto.rain.com To: uspoerlein@gmail.com Cc: freebsd-hackers@freebsd.org Subject: Re: /dev/dsp* & /dev/audio* devices not present Message-ID: <49693902.0x2OQspLPLnuQLwg%perryh@pluto.rain.com> In-Reply-To: <20090110185135.GB83079@roadrunner.spoerlein.net> References: <20090107181032.GA2808@rebelion.Sisis.de> <1231398405.2842.1.camel@daemon2.partygaming.local> <20090108080708.GE1462@roadrunner.spoerlein.net> <4966e5b7.sTBBp%2BJY%2BDDMKG47%perryh@pluto.rain.com> <20090109204014.GA83381@keira.kiwi-computer.com> <496892aa.n9QVqyhWypsSmeIU%perryh@pluto.rain.com> <20090110185135.GB83079@roadrunner.spoerlein.net>
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Ulrich Spoerlein <gmail.com!uspoerlein@agora.rdrop.com> wrote: > I cannot really comment on the devfs(4) design issues, > and quite frankly it hasn't bothered my thus far. It evidently inconvenienced the OP. > Just another little quirk you get to remember. If we followed that line of reasoning to its logical conclusion we would eliminate POLA entirely. > > IMO it violates POLA, if not POSIX, for open(2) to succeed when > > applied to a name which, according to readdir(2), does not > > exist; and it is suboptimal to have "stealth" drivers whose > > availability for use cannot be discovered by examining /dev. > > You forgot directories with --x permissions. You can open many > files inside them, but readdir(2) will get you nowhere. So this > is a poor standard by which to judge devfs(4) device cloning. There are at least two problems with that analysis: * /dev does not ordinarily have --x permissions. Even if I amended the principle to allow for that case, it would not affect its application to this case. * readdir works for root, even in directories with --x permissions. For example: $ mkdir test $ touch test/file $ ls -la test total 4 drwxr-xr-x 2 perryh perryh 512 Jan 10 15:39 . drwxr-xr-x 3 perryh perryh 512 Jan 10 15:39 .. -rw-r--r-- 1 perryh perryh 0 Jan 10 15:39 file $ chmod 111 test $ ls -ld test d--x--x--x 2 perryh perryh 512 Jan 10 15:39 test $ ls -la test total 0 ls: test: Permission denied # ls -la test total 4 d--x--x--x 2 perryh perryh 512 Jan 10 15:39 . drwxr-xr-x 3 perryh perryh 512 Jan 10 15:39 .. -rw-r--r-- 1 perryh perryh 0 Jan 10 15:39 file
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