Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [patch 6/7] um: Convert mmapper to unlocked_ioctl | Date | Fri, 16 Oct 2009 21:42:50 +0200 |
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On Thursday 15 October 2009, Alan Cox wrote: > On Thu, 15 Oct 2009 15:00:34 +0200 > Arnd Bergmann <arndbergmann@googlemail.com> wrote: > > > However, returning -ENOIOCTLCMD from an *unlocked_ioctl* function > > automatically gets turned into -EINVAL. It does this to allow > > the same functions to be used for unlocked_ioctl and compat_ioctl. > > In effect, this patch is functionally identical to removing the > > ioctl function, which I think is what should be done here. > > That is wrong. > > SuS requires an unknown ioctl code returns -ENOTTY. If the code is > currently remapping it to EINVAL then it wants fixing.
Right, I forgot about the EINVAL/ENOTTY difference. The code currently returns -ENOIOCTLCMD, which is worse. Thomas' patch makes it return -EINVAL, which as you said is still wrong. Removing the ioctl function will do the right thing and return -ENOTTY, so that should be done here in um/mmapper, with an appropriate changelog.
For the common code in fs/ioctl.c, I think the current behaviour is correct. It returns -EINVAL if the driver returns -ENOIOCTLCMD, iow "the request [...] argument is not valid for this device", as specified by http://www.opengroup.org/onlinepubs/009695399/functions/ioctl.html.
Drivers returning ENOIOCTLCMD for every request are broken and should be changed to have no ioctl function.
Arnd <><
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