1 files changed, 168 insertions, 0 deletions

diff --git a/kernel/kfifo.c b/kernel/kfifo.c
new file mode 100644
index 000000000000..179baafcdd96
--- /dev/null
+++ b/kernel/kfifo.c
@@ -0,0 +1,168 @@
+/*
+ * A simple kernel FIFO implementation.
+ *
+ * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/kfifo.h>
+
+/**
+ * kfifo_init - allocates a new FIFO using a preallocated buffer
+ * @buffer: the preallocated buffer to be used.
+ * @size: the size of the internal buffer, this have to be a power of 2.
+ * @gfp_mask: get_free_pages mask, passed to kmalloc()
+ * @lock: the lock to be used to protect the fifo buffer
+ *
+ * Do NOT pass the kfifo to kfifo_free() after use ! Simply free the
+ * struct kfifo with kfree().
+ */
+struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
+                         unsigned int __nocast gfp_mask, spinlock_t *lock)
+{
+        struct kfifo *fifo;
+
+        /* size must be a power of 2 */
+        BUG_ON(size & (size - 1));
+
+        fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
+        if (!fifo)
+                return ERR_PTR(-ENOMEM);
+
+        fifo->buffer = buffer;
+        fifo->size = size;
+        fifo->in = fifo->out = 0;
+        fifo->lock = lock;
+
+        return fifo;
+}
+EXPORT_SYMBOL(kfifo_init);
+
+/**
+ * kfifo_alloc - allocates a new FIFO and its internal buffer
+ * @size: the size of the internal buffer to be allocated.
+ * @gfp_mask: get_free_pages mask, passed to kmalloc()
+ * @lock: the lock to be used to protect the fifo buffer
+ *
+ * The size will be rounded-up to a power of 2.
+ */
+struct kfifo *kfifo_alloc(unsigned int size, unsigned int __nocast gfp_mask, spinlock_t *lock)
+{
+        unsigned char *buffer;
+        struct kfifo *ret;
+
+        /*
+         * round up to the next power of 2, since our 'let the indices
+         * wrap' tachnique works only in this case.
+         */
+        if (size & (size - 1)) {
+                BUG_ON(size > 0x80000000);
+                size = roundup_pow_of_two(size);
+        }
+
+        buffer = kmalloc(size, gfp_mask);
+        if (!buffer)
+                return ERR_PTR(-ENOMEM);
+
+        ret = kfifo_init(buffer, size, gfp_mask, lock);
+
+        if (IS_ERR(ret))
+                kfree(buffer);
+
+        return ret;
+}
+EXPORT_SYMBOL(kfifo_alloc);
+
+/**
+ * kfifo_free - frees the FIFO
+ * @fifo: the fifo to be freed.
+ */
+void kfifo_free(struct kfifo *fifo)
+{
+        kfree(fifo->buffer);
+        kfree(fifo);
+}
+EXPORT_SYMBOL(kfifo_free);
+
+/**
+ * __kfifo_put - puts some data into the FIFO, no locking version
+ * @fifo: the fifo to be used.
+ * @buffer: the data to be added.
+ * @len: the length of the data to be added.
+ *
+ * This function copies at most 'len' bytes from the 'buffer' into
+ * the FIFO depending on the free space, and returns the number of
+ * bytes copied.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these functions.
+ */
+unsigned int __kfifo_put(struct kfifo *fifo,
+                         unsigned char *buffer, unsigned int len)
+{
+        unsigned int l;
+
+        len = min(len, fifo->size - fifo->in + fifo->out);
+
+        /* first put the data starting from fifo->in to buffer end */
+        l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
+        memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
+
+        /* then put the rest (if any) at the beginning of the buffer */
+        memcpy(fifo->buffer, buffer + l, len - l);
+
+        fifo->in += len;
+
+        return len;
+}
+EXPORT_SYMBOL(__kfifo_put);
+
+/**
+ * __kfifo_get - gets some data from the FIFO, no locking version
+ * @fifo: the fifo to be used.
+ * @buffer: where the data must be copied.
+ * @len: the size of the destination buffer.
+ *
+ * This function copies at most 'len' bytes from the FIFO into the
+ * 'buffer' and returns the number of copied bytes.
+ *
+ * Note that with only one concurrent reader and one concurrent
+ * writer, you don't need extra locking to use these functions.
+ */
+unsigned int __kfifo_get(struct kfifo *fifo,
+                         unsigned char *buffer, unsigned int len)
+{
+        unsigned int l;
+
+        len = min(len, fifo->in - fifo->out);
+
+        /* first get the data from fifo->out until the end of the buffer */
+        l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
+        memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
+
+        /* then get the rest (if any) from the beginning of the buffer */
+        memcpy(buffer + l, fifo->buffer, len - l);
+
+        fifo->out += len;
+
+        return len;
+}
+EXPORT_SYMBOL(__kfifo_get);