From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: linux1394-devel@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] firewire: cdev: return -ENOTTY for unimplemented ioctls, not -EINVAL
Date: Sat, 9 Jul 2011 16:42:26 +0200 [thread overview]
Message-ID: <20110709164226.519a81fe@stein> (raw)
On Jun 27 Linus Torvalds wrote:
> The correct error code for "I don't understand this ioctl" is ENOTTY.
> The naming may be odd, but you should think of that error value as a
> "unrecognized ioctl number, you're feeding me random numbers that I
> don't understand and I assume for historical reasons that you tried to
> do some tty operation on me".
[...]
> The EINVAL thing goes way back, and is a disaster. It predates Linux
> itself, as far as I can tell. You'll find lots of man-pages that have
> this line in it:
>
> EINVAL Request or argp is not valid.
>
> and it shows up in POSIX etc. And sadly, it generally shows up
> _before_ the line that says
>
> ENOTTY The specified request does not apply to the kind of object
> that the descriptor d references.
>
> so a lot of people get to the EINVAL, and never even notice the ENOTTY.
[...]
> At least glibc (and hopefully other C libraries) use a _string_ that
> makes much more sense: strerror(ENOTTY) is "Inappropriate ioctl for
> device"
So let's correct this in the <linux/firewire-cdev.h> ABI while it is
still young, relative to distributor adoption.
Side note: We return -ENOTTY not only on _IOC_TYPE or _IOC_NR mismatch,
but also on _IOC_SIZE mismatch. An ioctl with an unsupported size of
argument structure can be seen as an unsupported version of that ioctl.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: <stable@kernel.org>
---
drivers/firewire/core-cdev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: b/drivers/firewire/core-cdev.c
===================================================================
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1583,7 +1583,7 @@ static int dispatch_ioctl(struct client
if (_IOC_TYPE(cmd) != '#' ||
_IOC_NR(cmd) >= ARRAY_SIZE(ioctl_handlers) ||
_IOC_SIZE(cmd) > sizeof(buffer))
- return -EINVAL;
+ return -ENOTTY;
if (_IOC_DIR(cmd) == _IOC_READ)
memset(&buffer, 0, _IOC_SIZE(cmd));
--
Stefan Richter
-=====-==-== -=== -=--=
http://arcgraph.de/sr/
next reply other threads:[~2011-07-09 14:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-09 14:42 Stefan Richter [this message]
2011-07-09 14:43 ` [PATCH] firewire: cdev: prevent race between first get_info ioctl and bus reset event queuing Stefan Richter
2011-07-09 14:47 ` [PATCH] firewire: cdev: ABI documentation enhancements Stefan Richter
2011-07-09 14:48 ` [PATCH] firewire: document the sysfs ABIs Stefan Richter
2011-07-09 15:05 ` [PATCH] firewire: cdev: ABI documentation enhancements Stefan Richter
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