Hi Sakari,
Em 26-06-2011 12:40, Sakari Ailus escreveu:
> Mauro Carvalho Chehab wrote:
>> Currently, -EINVAL is used to return either when an IOCTL is not
>> implemented, or if the ioctl was not implemented.
>
> Hi Mauro,
>
> Thanks for the patch.
>
> The V4L2 core probably should return -ENOIOCTLCMD when an IOCTL isn't implemented, but as long as vfs_ioctl() would stay as it is, the user space would still get -EINVAL. Or is vfs_ioctl() about to change?
>
> fs/ioctl.c:
> ----8<-----------
> static long vfs_ioctl(struct file *filp, unsigned int cmd,
> unsigned long arg)
> {
> int error = -ENOTTY;
>
> if (!filp->f_op || !filp->f_op->unlocked_ioctl)
> goto out;
>
> error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
> if (error == -ENOIOCTLCMD)
> error = -EINVAL;
> out:
> return error;
> }
> ----8<-----------
>
Good catch!
At the recent git history, the return for -ENOIOCTLCMD were modified
by this changeset:
commit b19dd42faf413b4705d4adb38521e82d73fa4249
Author: Arnd Bergmann <arnd@xxxxxxxx>
Date: Sun Jul 4 00:15:10 2010 +0200
bkl: Remove locked .ioctl file operation
...
@@ -39,21 +38,12 @@ static long vfs_ioctl(struct file *filp, unsigned int cmd,
{
int error = -ENOTTY;
- if (!filp->f_op)
+ if (!filp->f_op || !filp->f_op->unlocked_ioctl)
goto out;
- if (filp->f_op->unlocked_ioctl) {
- error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
- if (error == -ENOIOCTLCMD)
- error = -EINVAL;
- goto out;
- } else if (filp->f_op->ioctl) {
- lock_kernel();
- error = filp->f_op->ioctl(filp->f_path.dentry->d_inode,
- filp, cmd, arg);
- unlock_kernel();
...
Before Arnd's patch, locked ioctl's were returning -ENOIOCTLCMD, and
unlocked ones were returning -EINVAL. Now, the return of -ENOIOCTLCMD
doesn't go to userspace anymore. IMO, that's wrong and can cause
regressions, as some subsystems like DVB were returning -ENOIOCTLCMD
to userspace.
The right fix would be to remove this from fs:
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 1d9b9fc..802fbbd 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -41,8 +41,6 @@ static long vfs_ioctl(struct file *filp, unsigned int cmd,
goto out;
error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
- if (error == -ENOIOCTLCMD)
- error = -EINVAL;
out:
return error;
}
However, the replacement from -EINVAL to -ENOIOCTLCMD is there since 2.6.12 for
unlocked_ioctl:
$ git blame b19dd42f^1 fs/ioctl.c
...
^1da177e (Linus Torvalds 2005-04-16 15:20:36 -0700 46) error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
^1da177e (Linus Torvalds 2005-04-16 15:20:36 -0700 47) if (error == -ENOIOCTLCMD)
^1da177e (Linus Torvalds 2005-04-16 15:20:36 -0700 48) error = -EINVAL;
Linus,
what would be the expected behaviour?
Thanks,
Mauro
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