Messages in this thread | | | From | David Lang <> | Date | Mon, 21 May 2001 09:26:39 -0700 (PDT) | Subject | Re: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH]device arguments from lookup) |
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what makes you think it's safe to say there's only one floppy drive?
David Lang
On Mon, 21 May 2001, Oliver Xymoron wrote:
> On Sat, 19 May 2001, Alexander Viro wrote: > > > Let's distinguish between per-fd effects (that's what name in > > open(name, flags) is for - you are asking for descriptor and telling > > what behaviour do you want for IO on it) and system-wide side effects. > > > > IMO encoding the former into name is perfectly fine, and no write on > > another file can be sanely used for that purpose. For the latter, though, > > we need to write commands into files and here your miscdevices (or procfs > > files, or /dev/foo/ctl - whatever) is needed. > > I'm a little skeptical about the necessity of these per-fd effects in the > first place - after all, Plan 9 does without them. There's only one > floppy drive, yes? No concurrent users of serial ports? The counter that > comes to mind is sound devices supporting multiple opens, but I think > esound and friends are a better solution to that problem. > > What I'd like to see: > > - An interface for registering an array of related devices (almost always > two: raw and ctl) and their legacy device numbers with a single userspace > callout that does whatever /dev/ creation needs to be done. Thus, naming > and permissions live in user space. No "device node is also a directory" > weirdness which is overkill in the vast majority of cases. No kernel names > or permissions leaking into userspace. > > - An unregister_devices that does the same, giving userspace a > chance to persist permissions, etc. > > - A userspace program that keeps a mapping of kernel names to /dev/ names, > permissions, etc. > > - An autofs hook that does the reverse mapping for running with modules > (possibly calling modprobe directly) > > Possible future extension: > > - Allow exporting proc as a large collection of devices. Manage /proc in > userspace on a tmpfs. > > -- > "Love the dolphins," she advised him. "Write by W.A.S.T.E.." > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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