Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964796Ab2HIM4p (ORCPT ); Thu, 9 Aug 2012 08:56:45 -0400 Received: from hqemgate03.nvidia.com ([216.228.121.140]:14190 "EHLO hqemgate03.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932262Ab2HIM4n convert rfc822-to-8bit (ORCPT ); Thu, 9 Aug 2012 08:56:43 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Thu, 09 Aug 2012 05:51:15 -0700 Date: Thu, 9 Aug 2012 15:56:24 +0300 From: Hiroshi Doyu To: Greg Kroah-Hartman , Felipe Balbi CC: "iommu@lists.linux-foundation.org" , "linux-tegra@vger.kernel.org" , Al Viro , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] debugfs: Allow debugfs_create_dir() to take data Message-ID: <20120809155624.b781edae9efa7c51faf6c31c@nvidia.com> In-Reply-To: <20120808133427.GA14417@kroah.com> References: <1344407073-12030-1-git-send-email-hdoyu@nvidia.com> <1344407073-12030-2-git-send-email-hdoyu@nvidia.com> <20120808133427.GA14417@kroah.com> X-Mailer: Sylpheed 3.2.0beta3 (GTK+ 2.24.6; x86_64-pc-linux-gnu) X-NVConfidentiality: public MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4559 Lines: 118 Hi Greg, Felipe, On Wed, 8 Aug 2012 15:34:27 +0200 Greg Kroah-Hartman wrote: > On Wed, Aug 08, 2012 at 09:24:32AM +0300, Hiroshi Doyu wrote: > > Add __debugfs_create_dir(), which takes data passed from caller. > > Why? > > > Signed-off-by: Hiroshi Doyu > > --- > > fs/debugfs/inode.c | 7 ++++--- > > include/linux/debugfs.h | 9 ++++++++- > > 2 files changed, 12 insertions(+), 4 deletions(-) ..... > What are you trying to do here? This patch doesn't look right at all. I missed to send the cover letter of this patch series to LKML, which explained the background. I attached that cover letter below. Please read the following explanation too. The point was that, since directory hierarchy itself already has the necessary info, like parent <- child relationships, among each entities(here, smmu?, mc?, cache{tlb,ptc}), I just wanted to avoid to have those *residual* info embedded in normal data hierarchy, because cache{tlb,ptc} is used only in debugfs, not in the normal path. With directory/file hierarchy, we could get necessary data at any time on-the-fly. OTOH, if debugfs has the assumption that it has to be always projected from the existing data hierarchy, I should fix to have the same hierarchy in entities(here, smmu?, mc?, cache{tlb,ptc}), as Felipe pointed out in another thread. It might not be so bad that debugfs has the ability to manage its own hierarchy with i_private, apart from the original data hierarchy too. In our case, cache{tlb,ptc} data is used only for debugfs. They don't have to be in the normal data hierarchy. This depends on the above assumption, does debugfs have to be always projected from the normal data hierarchy? The original tegra smmu debugfs patch is: http://lists.linuxfoundation.org/pipermail/iommu/2012-August/004507.html Here's the original missed cover letter: Subject:[RFC][PATCH 0/2] debugfs: Allow debugfs_create_dir() to take data from caller From: Hiroshi Doyu To: Hiroshi Doyu CC: "iommu@lists.linux-foundation.org" , "linux-tegra@vger.kernel.org" , Al Viro Date: Wed, 8 Aug 2012 08:24:31 +0200 Thread-Index: Ac11LoTHb+fK/MOMRX2RFTvtP89jeg== Accept-Language: en-US, en-CA, fi-FI The commit c3b1a35 "debugfs: make sure that debugfs_create_file() gets used only for regulars" doesn't allow to use debugfs_create_file() for creating directory, and the current debugfs_create_dir() cannot take the private data from caller. There are some cases that we want to pass some client data to dir, especially when dir is nested deeply. We can work around to pass all necessary data with some invented data structure to the end files, but if directory itself had private data, we could avoid to introduce new structures just to pass data to end files. For example, tegra iommu(smmu) case, debugfs structure could be as below. sys/ └── kernel └── debug ├── smmu.0 │   ├── mc │   │   ├── ptc │   │   └── tlb │   └── mc0 │   ├── ptc │   └── tlb └── smmu.1 ├── mc │   ├── ptc │   └── tlb ├── mc0 │   ├── ptc │   └── tlb └── mc1 ├── ptc └── tlb The end files, {ptc,tlb} depend on which mc? to belong to, and which smmu.? to belong to. The parent data can be accessed from those end files if necessary. dent = d_find_alias(s->private); cache = (int)dent->d_inode->i_private; mc = (int)dent->d_parent->d_inode->i_private; smmu = dent->d_parent->d_parent->d_inode->i_private; The original tegra smmu debugfs patch is: http://lists.linuxfoundation.org/pipermail/iommu/2012-August/004507.html Hiroshi Doyu (2): debugfs: Allow debugfs_create_dir() to take data iommu/tegra: smmu: Use __debugfs_create_dir drivers/iommu/tegra-smmu.c | 4 +--- fs/debugfs/inode.c | 7 ++++--- include/linux/debugfs.h | 9 ++++++++- 3 files changed, 13 insertions(+), 7 deletions(-) -- 1.7.5.4 -- 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/