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authorStefani Seibold <stefani@seibold.net>2009-12-21 14:37:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-22 14:17:56 -0800
commita121f24accac1600bf5b6fb1e12eeabdfed7cb1a (patch)
tree24a3bb527e50304677785dbb390dd5ff838c94e8 /kernel
parent37bdfbbfaab47811fcec84dff23c4e8da1a09f9e (diff)
downloadvexpress-lsk-a121f24accac1600bf5b6fb1e12eeabdfed7cb1a.tar.gz
kfifo: add kfifo_skip, kfifo_from_user and kfifo_to_user
Add kfifo_reset_out() for save lockless discard the fifo output Add kfifo_skip() to skip a number of output bytes Add kfifo_from_user() to copy user space data into the fifo Add kfifo_to_user() to copy fifo data to user space Signed-off-by: Stefani Seibold <stefani@seibold.net> Acked-by: Greg Kroah-Hartman <gregkh@suse.de> Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com> Acked-by: Andi Kleen <ak@linux.intel.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kfifo.c139
1 files changed, 123 insertions, 16 deletions
diff --git a/kernel/kfifo.c b/kernel/kfifo.c
index d659442e73f..2a78425ef67 100644
--- a/kernel/kfifo.c
+++ b/kernel/kfifo.c
@@ -26,6 +26,7 @@
#include <linux/err.h>
#include <linux/kfifo.h>
#include <linux/log2.h>
+#include <linux/uaccess.h>
static void _kfifo_init(struct kfifo *fifo, unsigned char *buffer,
unsigned int size)
@@ -100,6 +101,21 @@ void kfifo_free(struct kfifo *fifo)
EXPORT_SYMBOL(kfifo_free);
/**
+ * kfifo_skip - skip output data
+ * @fifo: the fifo to be used.
+ * @len: number of bytes to skip
+ */
+void kfifo_skip(struct kfifo *fifo, unsigned int len)
+{
+ if (len < kfifo_len(fifo)) {
+ __kfifo_add_out(fifo, len);
+ return;
+ }
+ kfifo_reset_out(fifo);
+}
+EXPORT_SYMBOL(kfifo_skip);
+
+/**
* kfifo_in - puts some data into the FIFO
* @fifo: the fifo to be used.
* @from: the data to be added.
@@ -115,6 +131,7 @@ EXPORT_SYMBOL(kfifo_free);
unsigned int kfifo_in(struct kfifo *fifo,
const unsigned char *from, unsigned int len)
{
+ unsigned int off;
unsigned int l;
len = min(len, fifo->size - fifo->in + fifo->out);
@@ -126,21 +143,16 @@ unsigned int kfifo_in(struct kfifo *fifo,
smp_mb();
+ off = __kfifo_off(fifo, fifo->in);
+
/* 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)), from, l);
+ l = min(len, fifo->size - off);
+ memcpy(fifo->buffer + off, from, l);
/* then put the rest (if any) at the beginning of the buffer */
memcpy(fifo->buffer, from + l, len - l);
- /*
- * Ensure that we add the bytes to the kfifo -before-
- * we update the fifo->in index.
- */
-
- smp_wmb();
-
- fifo->in += len;
+ __kfifo_add_in(fifo, len);
return len;
}
@@ -161,6 +173,7 @@ EXPORT_SYMBOL(kfifo_in);
unsigned int kfifo_out(struct kfifo *fifo,
unsigned char *to, unsigned int len)
{
+ unsigned int off;
unsigned int l;
len = min(len, fifo->in - fifo->out);
@@ -172,22 +185,116 @@ unsigned int kfifo_out(struct kfifo *fifo,
smp_rmb();
+ off = __kfifo_off(fifo, 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(to, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
+ l = min(len, fifo->size - off);
+ memcpy(to, fifo->buffer + off, l);
/* then get the rest (if any) from the beginning of the buffer */
memcpy(to + l, fifo->buffer, len - l);
+ __kfifo_add_out(fifo, len);
+
+ return len;
+}
+EXPORT_SYMBOL(kfifo_out);
+
+/**
+ * kfifo_from_user - puts some data from user space into the FIFO
+ * @fifo: the fifo to be used.
+ * @from: pointer to the data to be added.
+ * @len: the length of the data to be added.
+ *
+ * This function copies at most @len bytes from the @from into the
+ * FIFO depending 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_from_user(struct kfifo *fifo,
+ const void __user *from, unsigned int len)
+{
+ unsigned int off;
+ unsigned int l;
+ int ret;
+
+ len = min(len, fifo->size - fifo->in + fifo->out);
+
/*
- * Ensure that we remove the bytes from the kfifo -before-
- * we update the fifo->out index.
+ * Ensure that we sample the fifo->out index -before- we
+ * start putting bytes into the kfifo.
*/
smp_mb();
- fifo->out += len;
+ off = __kfifo_off(fifo, fifo->in);
+
+ /* first put the data starting from fifo->in to buffer end */
+ l = min(len, fifo->size - off);
+ ret = copy_from_user(fifo->buffer + off, from, l);
+
+ if (unlikely(ret))
+ return l - ret;
+
+ /* then put the rest (if any) at the beginning of the buffer */
+ ret = copy_from_user(fifo->buffer, from + l, len - l);
+
+ if (unlikely(ret))
+ return len - ret;
+
+ __kfifo_add_in(fifo, len);
return len;
}
-EXPORT_SYMBOL(kfifo_out);
+EXPORT_SYMBOL(kfifo_from_user);
+
+/**
+ * kfifo_to_user - gets data from the FIFO and write it to user space
+ * @fifo: the fifo to be used.
+ * @to: 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
+ * @to 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_to_user(struct kfifo *fifo,
+ void __user *to, unsigned int len)
+{
+ unsigned int off;
+ unsigned int l;
+ int ret;
+
+ len = min(len, fifo->in - fifo->out);
+
+ /*
+ * Ensure that we sample the fifo->in index -before- we
+ * start removing bytes from the kfifo.
+ */
+
+ smp_rmb();
+
+ off = __kfifo_off(fifo, fifo->out);
+
+ /* first get the data from fifo->out until the end of the buffer */
+ l = min(len, fifo->size - off);
+ ret = copy_to_user(to, fifo->buffer + off, l);
+
+ if (unlikely(ret))
+ return l - ret;
+
+ /* then get the rest (if any) from the beginning of the buffer */
+ ret = copy_to_user(to + l, fifo->buffer, len - l);
+
+ if (unlikely(ret))
+ return len - ret;
+
+ __kfifo_add_out(fifo, len);
+
+ return len;
+}
+EXPORT_SYMBOL(kfifo_to_user);
+