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Message-ID: <49E2E5CD.9050402@cn.fujitsu.com> Date: Mon, 13 Apr 2009 15:12:13 +0800 From: Shen Feng <shen@...fujitsu.com> To: gregkh@...e.de, Andrew Morton <akpm@...ux-foundation.org> CC: linux-kernel@...r.kernel.org Subject: [PATCH] doc: add documentation for debugfs debugfs is used as a virtual filesystem devoted to debugging information. But it's not documented in Documentation/filesystems. Add one for it. The content is mainly from http://lwn.net/Articles/115405/ Signed-off-by: Shen Feng <shen@...fujitsu.com> --- Documentation/filesystems/debugfs.txt | 51 +++++++++++++++++++++++++++++++++ 1 files changed, 51 insertions(+), 0 deletions(-) create mode 100644 Documentation/filesystems/debugfs.txt diff --git a/Documentation/filesystems/debugfs.txt b/Documentation/filesystems/debugfs.txt new file mode 100644 index 0000000..112cf0c --- /dev/null +++ b/Documentation/filesystems/debugfs.txt @@ -0,0 +1,51 @@ + Debugfs - a virtual filesystem devoted to debugging information + +Debugfs is a virtual filesystem devoted to debugging information. Debugfs is +intended to be a relatively easy and lightweight subsystem which gracefully +disappears when configured out of the kernel. + +Traditionally debugfs is supposed to be mounted at /sys/kernel/debug with the +following command: + + # mount -t debugfs none /sys/kernel/debug/ + +A developer wishing to use debugfs starts by creating a directory within the +filesystem: + + struct dentry *debugfs_create_dir(const char *name, + struct dentry *parent); + +The parent argument will usually be NULL, causing the directory to be created +in the debugfs root. If debugfs is not configured into the system, the return +value is -ENODEV; a NULL return, instead, indicates some other sort of error. + +The general-purpose function for creating a file in debugfs is: + + struct dentry *debugfs_create_file(const char *name, mode_t mode, + struct dentry *parent, void *data, + struct file_operations *fops); + +The structure pointed to by fops should, of course, contain pointers to the +functions which implement the actual operations on the file. In many cases, +most of those functions can be the helpers provided by seq_file, making the +task of exporting a file easy. + +Some additional helpers have been provided to make exporting a single value as +easy as possible: + + struct dentry *debugfs_create_u8(const char *name, mode_t mode, + struct dentry *parent, u8 *value); + struct dentry *debugfs_create_u16(const char *name, mode_t mode, + struct dentry *parent, u16 *value); + struct dentry *debugfs_create_u32(const char *name, mode_t mode, + struct dentry *parent, u32 *value); + struct dentry *debugfs_create_bool(const char *name, mode_t mode, + struct dentry *parent, u32 *value); + +Debugfs does not automatically clean up files when a module shuts down, so, +for every file or directory created with the above functions, there must be a +call to: + + void debugfs_remove(struct dentry *dentry); + +See Documentation/DocBook/filesystems for more details. -- 1.6.0.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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