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Documentation: Update filesystems/debugfs.txt

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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: Wang Long <long.wanglong@huawei.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Wang Long 2015-07-16 06:31:16 +00:00 committed by Jonathan Corbet
parent a10726bb54
commit 9e1aa7c888
1 changed files with 40 additions and 0 deletions
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40
Documentation/filesystems/debugfs.txt
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@ -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 the return value will be a dentry pointer to the created file, NULL for
error, or ERR_PTR(-ENODEV) if debugfs support is missing. 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 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 actually necessary; the debugfs code provides a number of helper functions
for simple situations. Files containing a single integer value can be 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 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. 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 Another option is exporting a block of arbitrary binary data, with
this structure and function: 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 using __stringify, and a number of register names (macros) are actually
byte offsets over a base for the register block. 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: There are a couple of other directory-oriented helper functions: