From 5bf2b19320ec31d094d7370fdf536f7fd91fd799 Mon Sep 17 00:00:00 2001 From: Stefani Seibold Date: Tue, 10 Aug 2010 18:03:39 -0700 Subject: kfifo: add example files to the kernel sample directory Add four examples to the kernel sample directory. It shows how to handle: - a byte stream fifo - a integer type fifo - a dynamic record sized fifo - the fifo DMA functions [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Stefani Seibold Cc: Greg KH Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- samples/kfifo/record-example.c | 167 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 samples/kfifo/record-example.c (limited to 'samples/kfifo/record-example.c') diff --git a/samples/kfifo/record-example.c b/samples/kfifo/record-example.c new file mode 100644 index 00000000000..32c6e0bda74 --- /dev/null +++ b/samples/kfifo/record-example.c @@ -0,0 +1,167 @@ +/* + * Sample dynamic sized record fifo implementation + * + * Copyright (C) 2010 Stefani Seibold + * + * Released under the GPL version 2 only. + * + */ + +#include +#include +#include +#include +#include + +/* + * This module shows how to create a variable sized record fifo. + */ + +/* fifo size in elements (bytes) */ +#define FIFO_SIZE 128 + +/* name of the proc entry */ +#define PROC_FIFO "record-fifo" + +/* lock for procfs read access */ +static DEFINE_MUTEX(read_lock); + +/* lock for procfs write access */ +static DEFINE_MUTEX(write_lock); + +/* + * define DYNAMIC in this example for a dynamically allocated fifo. + * + * Otherwise the fifo storage will be a part of the fifo structure. + */ +#if 0 +#define DYNAMIC +#endif + +/* + * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a + * length between 0 and 255 bytes. + * + * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a + * length between 0 and 65535 bytes. + */ + +#ifdef DYNAMIC +struct kfifo_rec_ptr_1 test; + +#else +typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; + +static mytest test; +#endif + +static int __init testfunc(void) +{ + char buf[100]; + unsigned int i; + unsigned int ret; + struct { unsigned char buf[6]; } hello = { "hello" }; + + printk(KERN_INFO "record fifo test start\n"); + + kfifo_in(&test, &hello, sizeof(hello)); + + /* show the size of the next record in the fifo */ + printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); + + /* put in variable length data */ + for (i = 0; i < 10; i++) { + memset(buf, 'a' + i, i + 1); + kfifo_in(&test, buf, i + 1); + } + + printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); + + /* show the first record without removing from the fifo */ + ret = kfifo_out_peek(&test, buf, sizeof(buf)); + if (ret) + printk(KERN_INFO "%.*s\n", ret, buf); + + /* print out all records in the fifo */ + while (!kfifo_is_empty(&test)) { + ret = kfifo_out(&test, buf, sizeof(buf)); + printk(KERN_INFO "%.*s\n", ret, buf); + } + + return 0; +} + +static ssize_t fifo_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + int ret; + unsigned int copied; + + if (mutex_lock_interruptible(&write_lock)) + return -ERESTARTSYS; + + ret = kfifo_from_user(&test, buf, count, &copied); + + mutex_unlock(&write_lock); + + return ret ? ret : copied; +} + +static ssize_t fifo_read(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + int ret; + unsigned int copied; + + if (mutex_lock_interruptible(&read_lock)) + return -ERESTARTSYS; + + ret = kfifo_to_user(&test, buf, count, &copied); + + mutex_unlock(&read_lock); + + return ret ? ret : copied; +} + +static const struct file_operations fifo_fops = { + .owner = THIS_MODULE, + .read = fifo_read, + .write = fifo_write, +}; + +static int __init example_init(void) +{ +#ifdef DYNAMIC + int ret; + + ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); + if (ret) { + printk(KERN_ERR "error kfifo_alloc\n"); + return ret; + } +#else + INIT_KFIFO(test); +#endif + testfunc(); + + if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { +#ifdef DYNAMIC + kfifo_free(&test); +#endif + return -ENOMEM; + } + return 0; +} + +static void __exit example_exit(void) +{ + remove_proc_entry(PROC_FIFO, NULL); +#ifdef DYNAMIC + kfifo_free(&test); +#endif +} + +module_init(example_init); +module_exit(example_exit); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Stefani Seibold "); -- cgit v1.2.3-70-g09d2