Re: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH] device arguments from lookup)

Linus Torvalds
2001-05-19T18:14:37Z

On Sat, 19 May 2001, Alexander Viro wrote:
>
> Folks, before you get all excited about cramming side effects into
> open(2), consider the following case:

Your argument is stupid, imnsho.

Side-effects are perfectly fine if they are _local_ to the file
descriptor. Your example is contrieved and idiotic.

Filename extensions would not replace ioctl's. But they are wonderful ways
to avoid unnecessary binary name-spaces, like the ones we have with
"callout" TTY names, and the one that the fb people had.

For example, do a "ls -l /dev/fd0*", and ponder. Also, realize that we
have these hard-coded names in _addition_ to the magic ioctl to set even
more parameters. These are all stupid and bad, and it would have been a
_lot_ cleaner to be able to do

open("/dev/fd0/H1440", O_RDWR)..

or

open("/dev/fd0/HD,18,85", O_RDWD)

to open special non-standard high-density modes.

We already did this, in a very limited and stupid way, by encoding the
minor number and generating a standard naming scheme. We can do the same
thing in a _much_ more generic way by just realizing that we wanted the
open to be name-based in the first place.

These are _not_ side effects. They are very much naming conventions. If I
want to open a the floppy in one of the special extended modes, it makes a
LOT more sense to just open it with the naming, than to open a "generic"
floppy device only to them use a magic and very unreadable ioctl to set
the mode of the device.

In short, I don't buy your arguments for one single second.

Linus