From: Al Viro <email@example.com> To: Tomas Carnecky <firstname.lastname@example.org> Cc: Miklos Szeredi <email@example.com>, firstname.lastname@example.org, email@example.com Subject: Re: Problem with ioctl command TCGETS Date: Sun, 28 Nov 2004 14:05:52 +0000 Message-ID: <20041128140552.GD26051@parcelfarce.linux.theplanet.co.uk> (raw) In-Reply-To: <41A9D093.firstname.lastname@example.org> On Sun, Nov 28, 2004 at 02:20:19PM +0100, Tomas Carnecky wrote: > But then you'd have to open another file :( Correct, but not necessary on sysfs. > And what about somethink like: > cdrom_fd = open("/dev/cdrom", O_RDWR) > cdrom_param_fd = get_param_fd(cdrom_fd) /* a new syscall */ > Now read/write to this param fd. > And two new entries in the struct file_operations: > write_param([same args as write]) > read_param([same args as read]) That assumes that there is any sort of uniform semantics for these operations. There isn't. Moreover, you are insisting on pushing all of them into the same channel; not a good idea since the set of things done with ioctls tends to consist of several unrelated classes, often coming from a bunch of unrelated subsystems. There is no mechanical replacement for ioctl(); the nature of its problems is that we have a random mix of unrelated operations bumped into one pile. Take a look at e.g. networking ioctls. Most of them openly ignores the descriptor used to issue an ioctl - more often then not the first thing they do is to peek into the passed data structure and go looking for the real object we are going to operate upon; e.g. find an interface by name. Of course it's bogus; any sane modification of that API would have the object selected by the opened file we are passing to it. And no, we have no chance in hell to rewrite all userland code that uses these suckers, so we are stuck with them for all forseeable future. UCB folks had no taste, film at 11... For more or less common (read: implemented by more than a couple of drivers) ioctls we have to keep them anyway; for the stuff where we really stand a chance of doing some kind of changes (including the new operations) we can bloody well do splitup by files that would match the nature of operations. Which leaves the "get me secondary channel by fd" kind of operations without any uses.
next prev parent reply index Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-11-28 0:22 Ozan Eren Bilgen 2004-11-28 0:39 ` Al Viro 2004-11-28 9:59 ` Miklos Szeredi 2004-11-28 10:08 ` Jan Engelhardt 2004-11-28 10:18 ` Miklos Szeredi 2004-11-28 10:28 ` Bernd Eckenfels 2004-11-28 10:56 ` Wichert Akkerman 2004-11-28 11:52 ` Bernd Eckenfels 2004-11-28 11:22 ` Miklos Szeredi 2004-11-28 12:18 ` Al Viro 2004-11-28 12:32 ` Miklos Szeredi 2004-11-28 12:48 ` Al Viro 2004-11-28 12:52 ` Miklos Szeredi 2004-11-28 13:03 ` Al Viro 2004-11-28 14:30 ` Tomas Carnecky 2004-11-28 15:27 ` Al Viro 2004-11-28 18:23 ` Tomas Carnecky 2004-11-28 18:51 ` Miklos Szeredi 2004-12-10 4:01 ` Ingo Oeser 2004-11-28 13:20 ` Tomas Carnecky 2004-11-28 14:05 ` Al Viro [this message] 2004-11-28 13:07 ` Tomas Carnecky 2004-11-28 13:11 ` Al Viro 2004-11-28 13:19 ` Tomas Carnecky 2004-11-28 17:42 ` Alan Cox 2004-11-30 13:26 ` Pavel Machek 2004-11-30 15:46 ` Al Viro 2004-11-28 12:23 ` Bernd Eckenfels
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