1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * tracefs.h - a pseudo file system for activating tracing 4 * 5 * Based on debugfs by: 2004 Greg Kroah-Hartman <greg@kroah.com> 6 * 7 * Copyright (C) 2014 Red Hat Inc, author: Steven Rostedt <srostedt@redhat.com> 8 * 9 * tracefs is the file system that is used by the tracing infrastructure. 10 */ 11 12 #ifndef _TRACEFS_H_ 13 #define _TRACEFS_H_ 14 15 #include <linux/fs.h> 16 #include <linux/seq_file.h> 17 18 #include <linux/types.h> 19 20 struct file_operations; 21 22 #ifdef CONFIG_TRACING 23 24 struct eventfs_file; 25 26 /** 27 * eventfs_callback - A callback function to create dynamic files in eventfs 28 * @name: The name of the file that is to be created 29 * @mode: return the file mode for the file (RW access, etc) 30 * @data: data to pass to the created file ops 31 * @fops: the file operations of the created file 32 * 33 * The evetnfs files are dynamically created. The struct eventfs_entry array 34 * is passed to eventfs_create_dir() or eventfs_create_events_dir() that will 35 * be used to create the files within those directories. When a lookup 36 * or access to a file within the directory is made, the struct eventfs_entry 37 * array is used to find a callback() with the matching name that is being 38 * referenced (for lookups, the entire array is iterated and each callback 39 * will be called). 40 * 41 * The callback will be called with @name for the name of the file to create. 42 * The callback can return less than 1 to indicate that no file should be 43 * created. 44 * 45 * If a file is to be created, then @mode should be populated with the file 46 * mode (permissions) for which the file is created for. This would be 47 * used to set the created inode i_mode field. 48 * 49 * The @data should be set to the data passed to the other file operations 50 * (read, write, etc). Note, @data will also point to the data passed in 51 * to eventfs_create_dir() or eventfs_create_events_dir(), but the callback 52 * can replace the data if it chooses to. Otherwise, the original data 53 * will be used for the file operation functions. 54 * 55 * The @fops should be set to the file operations that will be used to create 56 * the inode. 57 * 58 * NB. This callback is called while holding internal locks of the eventfs 59 * system. The callback must not call any code that might also call into 60 * the tracefs or eventfs system or it will risk creating a deadlock. 61 */ 62 typedef int (*eventfs_callback)(const char *name, umode_t *mode, void **data, 63 const struct file_operations **fops); 64 65 /** 66 * struct eventfs_entry - dynamically created eventfs file call back handler 67 * @name: Then name of the dynamic file in an eventfs directory 68 * @callback: The callback to get the fops of the file when it is created 69 * 70 * See evenfs_callback() typedef for how to set up @callback. 71 */ 72 struct eventfs_entry { 73 const char *name; 74 eventfs_callback callback; 75 }; 76 77 struct eventfs_inode; 78 79 struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent, 80 const struct eventfs_entry *entries, 81 int size, void *data); 82 83 struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent, 84 const struct eventfs_entry *entries, 85 int size, void *data); 86 87 void eventfs_remove_events_dir(struct eventfs_inode *ei); 88 void eventfs_remove_dir(struct eventfs_inode *ei); 89 90 struct dentry *tracefs_create_file(const char *name, umode_t mode, 91 struct dentry *parent, void *data, 92 const struct file_operations *fops); 93 94 struct dentry *tracefs_create_dir(const char *name, struct dentry *parent); 95 96 void tracefs_remove(struct dentry *dentry); 97 98 struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent, 99 int (*mkdir)(const char *name), 100 int (*rmdir)(const char *name)); 101 102 bool tracefs_initialized(void); 103 104 #endif /* CONFIG_TRACING */ 105 106 #endif 107