Messages in this thread Patch in this message | | | Date | Sun, 26 Jun 2011 13:20:21 -0300 | From | Mauro Carvalho Chehab <> | Subject | Re: [PATCH] [media] v4l2 core: return -ENOIOCTLCMD if an ioctl doesn't exist |
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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@arndb.de> 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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