From 5392dda6e2b429cdf8d72dcbe36481372e1caa14 Mon Sep 17 00:00:00 2001 From: Stefan Richter Date: Sat, 9 Jul 2011 16:42:26 +0200 Subject: [PATCH] firewire: cdev: return -ENOTTY for unimplemented ioctls, not [ upstream commit d873d794235efa590ab3c94d5ee22bb1fab19ac4 ] -EINVAL 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 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 Cc: Signed-off-by: Andi Kleen --- drivers/firewire/core-cdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c index 56728dd1381e..5816c46e701d 100644 --- a/drivers/firewire/core-cdev.c +++ b/drivers/firewire/core-cdev.c @@ -1361,7 +1361,7 @@ static int dispatch_ioctl(struct client *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)); -- 2.39.2