From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Jones Subject: Re: [PATCH V3] seq_file: Document seq_open_private(), seq_release_private() Date: Tue, 26 Aug 2014 11:58:58 +0100 Message-ID: <53FC6872.3060800@codethink.co.uk> References: <1408362005-21504-1-git-send-email-rob.jones@codethink.co.uk> <53F1E879.2050302@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel@lists.codethink.co.uk, viro@ZenIV.linux.org.uk, ebiederm@xmission.com, ian.molton@codethink.co.uk To: Steven Whitehouse , linux-fsdevel@vger.kernel.org Return-path: In-Reply-To: <53F1E879.2050302@redhat.com> Sender: linux-doc-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Are there any other responses on this please? It seems pretty uncontentious. Maybe everyone was at LinuxCon last week. On 18/08/14 12:50, Steven Whitehouse wrote: > Hi, > > On 18/08/14 12:40, Rob Jones wrote: >> Despite the fact that these functions have been around for years, they >> are >> little used (only 15 uses in 13 files at the preseht time) even though >> many other files use work-arounds to achieve the same result. >> >> By documenting them, hopefully they will become more widely used. >> >> Signed-off-by: Rob Jones > Acked-by: Steven Whitehouse > > Steve. > >> --- >> Documentation/filesystems/seq_file.txt | 33 >> ++++++++++++++++++++++++++++++++ >> 1 file changed, 33 insertions(+) >> >> diff --git a/Documentation/filesystems/seq_file.txt >> b/Documentation/filesystems/seq_file.txt >> index a1e2e0d..420fc0d 100644 >> --- a/Documentation/filesystems/seq_file.txt >> +++ b/Documentation/filesystems/seq_file.txt >> @@ -226,6 +226,39 @@ be used for more than one file, you can store an >> arbitrary pointer in the >> private field of the seq_file structure; that value can then be >> retrieved >> by the iterator functions. >> +There is also a wrapper function to seq_open() called >> seq_open_private(). It >> +kmallocs a zero filled block of memory and stores a pointer to it in the >> +private field of the seq_file structure, returning 0 on success. The >> +block size is specified in a third parameter to the function, e.g.: >> + >> + static int ct_open(struct inode *inode, struct file *file) >> + { >> + return seq_open_private(file, &ct_seq_ops, >> + sizeof(struct mystruct)); >> + } >> + >> +There is also a variant function, __seq_open_private(), which is >> functionally >> +identical except that, if successful, it returns the pointer to the >> allocated >> +memory block, allowing further initialisation e.g.: >> + >> + static int ct_open(struct inode *inode, struct file *file) >> + { >> + struct mystruct *p = >> + __seq_open_private(file, &ct_seq_ops, sizeof(*p)); >> + >> + if (!p) >> + return -ENOMEM; >> + >> + p->foo = bar; /* initialize my stuff */ >> + ... >> + p->baz = true; >> + >> + return 0; >> + } >> + >> +A corresponding close function, seq_release_private() is available which >> +frees the memory allocated in the corresponding open. >> + >> The other operations of interest - read(), llseek(), and release() - >> are >> all implemented by the seq_file code itself. So a virtual file's >> file_operations structure will look like: > > > -- Rob Jones Codethink Ltd mailto:rob.jones@codethink.co.uk tel:+44 161 236 5575