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Diffstat (limited to 'samples/kfifo/record-example.c')
| -rw-r--r-- | samples/kfifo/record-example.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/samples/kfifo/record-example.c b/samples/kfifo/record-example.c new file mode 100644 index 000000000..e4087b2d3 --- /dev/null +++ b/samples/kfifo/record-example.c @@ -0,0 +1,202 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Sample dynamic sized record fifo implementation + * + * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net> + */ + +#include <linux/init.h> +#include <linux/module.h> +#include <linux/proc_fs.h> +#include <linux/mutex.h> +#include <linux/kfifo.h> + +/* + * 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_access); + +/* lock for procfs write access */ +static DEFINE_MUTEX(write_access); + +/* + * 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 const char *expected_result[] = { + "a", + "bb", + "ccc", + "dddd", + "eeeee", + "ffffff", + "ggggggg", + "hhhhhhhh", + "iiiiiiiii", + "jjjjjjjjjj", +}; + +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); + } + + /* skip first element of the fifo */ + printk(KERN_INFO "skip 1st element\n"); + kfifo_skip(&test); + + 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); + + /* check the correctness of all values in the fifo */ + i = 0; + while (!kfifo_is_empty(&test)) { + ret = kfifo_out(&test, buf, sizeof(buf)); + buf[ret] = '\0'; + printk(KERN_INFO "item = %.*s\n", ret, buf); + if (strcmp(buf, expected_result[i++])) { + printk(KERN_WARNING "value mismatch: test failed\n"); + return -EIO; + } + } + if (i != ARRAY_SIZE(expected_result)) { + printk(KERN_WARNING "size mismatch: test failed\n"); + return -EIO; + } + printk(KERN_INFO "test passed\n"); + + 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_access)) + return -ERESTARTSYS; + + ret = kfifo_from_user(&test, buf, count, &copied); + + mutex_unlock(&write_access); + if (ret) + return ret; + + return 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_access)) + return -ERESTARTSYS; + + ret = kfifo_to_user(&test, buf, count, &copied); + + mutex_unlock(&read_access); + if (ret) + return ret; + + return copied; +} + +static const struct proc_ops fifo_proc_ops = { + .proc_read = fifo_read, + .proc_write = fifo_write, + .proc_lseek = noop_llseek, +}; + +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 + if (testfunc() < 0) { +#ifdef DYNAMIC + kfifo_free(&test); +#endif + return -EIO; + } + + if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == 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 <stefani@seibold.net>"); |