Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151Ab1FZQU4 (ORCPT ); Sun, 26 Jun 2011 12:20:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10894 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754097Ab1FZQUj (ORCPT ); Sun, 26 Jun 2011 12:20:39 -0400 Message-ID: <4E075C45.3010200@redhat.com> Date: Sun, 26 Jun 2011 13:20:21 -0300 From: Mauro Carvalho Chehab User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110419 Red Hat/3.1.10-1.el6_0 Thunderbird/3.1.10 MIME-Version: 1.0 To: Sakari Ailus CC: Linux Media Mailing List , Linux Kernel Mailing List , Arnd Bergmann , Linus Torvalds Subject: Re: [PATCH] [media] v4l2 core: return -ENOIOCTLCMD if an ioctl doesn't exist References: <4E0519B7.3000304@redhat.com> <4E0752E0.5030901@iki.fi> In-Reply-To: <4E0752E0.5030901@iki.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3253 Lines: 105 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 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/