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Commit 9e1aa7c8 authored by Wang Long's avatar Wang Long Committed by Jonathan Corbet
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Documentation: Update filesystems/debugfs.txt 



This patch update the Documentation/filesystems/debugfs.txt
file. The main work is to add the description of the following
functions:
    debugfs_create_atomic_t
    debugfs_create_u32_array
    debugfs_create_devm_seqfile
    debugfs_create_file_size

Signed-off-by: default avatarWang Long <long.wanglong@huawei.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent a10726bb

Documentation/filesystems/debugfs.txt

+40 −0
Original line number Diff line number Diff line
@@ -51,6 +51,17 @@ operations should be provided; others can be included as needed. Again, 
the return value will be a dentry pointer to the created file, NULL for

error, or ERR_PTR(-ENODEV) if debugfs support is missing.



Create a file with an initial size, the following function can be used

instead:



    struct dentry *debugfs_create_file_size(const char *name, umode_t mode,

				struct dentry *parent, void *data,

				const struct file_operations *fops,

				loff_t file_size);



file_size is the initial file size. The other parameters are the same

as the function debugfs_create_file.



In a number of cases, the creation of a set of file operations is not

actually necessary; the debugfs code provides a number of helper functions

for simple situations.  Files containing a single integer value can be
@@ -100,6 +111,14 @@ A read on the resulting file will yield either Y (for non-zero values) or 
N, followed by a newline.  If written to, it will accept either upper- or

lower-case values, or 1 or 0.  Any other input will be silently ignored.



Also, atomic_t values can be placed in debugfs with:



    struct dentry *debugfs_create_atomic_t(const char *name, umode_t mode,

				struct dentry *parent, atomic_t *value)



A read of this file will get atomic_t values, and a write of this file

will set atomic_t values.



Another option is exporting a block of arbitrary binary data, with

this structure and function:
@@ -147,6 +166,27 @@ The "base" argument may be 0, but you may want to build the reg32 array 
using __stringify, and a number of register names (macros) are actually

byte offsets over a base for the register block.



If you want to dump an u32 array in debugfs, you can create file with:



    struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,

			struct dentry *parent,

			u32 *array, u32 elements);



The "array" argument provides data, and the "elements" argument is

the number of elements in the array. Note: Once array is created its

size can not be changed.



There is a helper function to create device related seq_file:



   struct dentry *debugfs_create_devm_seqfile(struct device *dev,

				const char *name,

				struct dentry *parent,

				int (*read_fn)(struct seq_file *s,

					void *data));



The "dev" argument is the device related to this debugfs file, and

the "read_fn" is a function pointer which to be called to print the

seq_file content.



There are a couple of other directory-oriented helper functions: