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Subject[PATCH 1/1] usb: gadget: u_serial: Use kfifo instead of homemade circular buffer
Date
The kernel FIFO implementation, kfifo, provides interfaces to manipulate
a first-in-first-out circular buffer. Use kfifo instead of the homemade
one to make the code more concise and readable.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/usb/gadget/function/u_serial.c | 192 +++++----------------------------
1 file changed, 24 insertions(+), 168 deletions(-)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 4d653d2..29436f7 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -26,6 +26,7 @@
#include <linux/module.h>
#include <linux/console.h>
#include <linux/kthread.h>
+#include <linux/kfifo.h>

#include "u_serial.h"

@@ -80,19 +81,11 @@
#define WRITE_BUF_SIZE 8192 /* TX only */
#define GS_CONSOLE_BUF_SIZE 8192

-/* circular buffer */
-struct gs_buf {
- unsigned buf_size;
- char *buf_buf;
- char *buf_get;
- char *buf_put;
-};
-
/* console info */
struct gscons_info {
struct gs_port *port;
struct task_struct *console_thread;
- struct gs_buf con_buf;
+ struct kfifo con_buf;
/* protect the buf and busy flag */
spinlock_t con_lock;
int req_busy;
@@ -122,7 +115,7 @@ struct gs_port {
struct list_head write_pool;
int write_started;
int write_allocated;
- struct gs_buf port_write_buf;
+ struct kfifo port_write_buf;
wait_queue_head_t drain_wait; /* wait while writes drain */
bool write_busy;
wait_queue_head_t close_wait;
@@ -154,144 +147,6 @@ static struct portmaster {

/*-------------------------------------------------------------------------*/

-/* Circular Buffer */
-
-/*
- * gs_buf_alloc
- *
- * Allocate a circular buffer and all associated memory.
- */
-static int gs_buf_alloc(struct gs_buf *gb, unsigned size)
-{
- gb->buf_buf = kmalloc(size, GFP_KERNEL);
- if (gb->buf_buf == NULL)
- return -ENOMEM;
-
- gb->buf_size = size;
- gb->buf_put = gb->buf_buf;
- gb->buf_get = gb->buf_buf;
-
- return 0;
-}
-
-/*
- * gs_buf_free
- *
- * Free the buffer and all associated memory.
- */
-static void gs_buf_free(struct gs_buf *gb)
-{
- kfree(gb->buf_buf);
- gb->buf_buf = NULL;
-}
-
-/*
- * gs_buf_clear
- *
- * Clear out all data in the circular buffer.
- */
-static void gs_buf_clear(struct gs_buf *gb)
-{
- gb->buf_get = gb->buf_put;
- /* equivalent to a get of all data available */
-}
-
-/*
- * gs_buf_data_avail
- *
- * Return the number of bytes of data written into the circular
- * buffer.
- */
-static unsigned gs_buf_data_avail(struct gs_buf *gb)
-{
- return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
-}
-
-/*
- * gs_buf_space_avail
- *
- * Return the number of bytes of space available in the circular
- * buffer.
- */
-static unsigned gs_buf_space_avail(struct gs_buf *gb)
-{
- return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
-}
-
-/*
- * gs_buf_put
- *
- * Copy data data from a user buffer and put it into the circular buffer.
- * Restrict to the amount of space available.
- *
- * Return the number of bytes copied.
- */
-static unsigned
-gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
-{
- unsigned len;
-
- len = gs_buf_space_avail(gb);
- if (count > len)
- count = len;
-
- if (count == 0)
- return 0;
-
- len = gb->buf_buf + gb->buf_size - gb->buf_put;
- if (count > len) {
- memcpy(gb->buf_put, buf, len);
- memcpy(gb->buf_buf, buf+len, count - len);
- gb->buf_put = gb->buf_buf + count - len;
- } else {
- memcpy(gb->buf_put, buf, count);
- if (count < len)
- gb->buf_put += count;
- else /* count == len */
- gb->buf_put = gb->buf_buf;
- }
-
- return count;
-}
-
-/*
- * gs_buf_get
- *
- * Get data from the circular buffer and copy to the given buffer.
- * Restrict to the amount of data available.
- *
- * Return the number of bytes copied.
- */
-static unsigned
-gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
-{
- unsigned len;
-
- len = gs_buf_data_avail(gb);
- if (count > len)
- count = len;
-
- if (count == 0)
- return 0;
-
- len = gb->buf_buf + gb->buf_size - gb->buf_get;
- if (count > len) {
- memcpy(buf, gb->buf_get, len);
- memcpy(buf+len, gb->buf_buf, count - len);
- gb->buf_get = gb->buf_buf + count - len;
- } else {
- memcpy(buf, gb->buf_get, count);
- if (count < len)
- gb->buf_get += count;
- else /* count == len */
- gb->buf_get = gb->buf_buf;
- }
-
- return count;
-}
-
-/*-------------------------------------------------------------------------*/
-
/* I/O glue between TTY (upper) and USB function (lower) driver layers */

/*
@@ -346,11 +201,11 @@ gs_send_packet(struct gs_port *port, char *packet, unsigned size)
{
unsigned len;

- len = gs_buf_data_avail(&port->port_write_buf);
+ len = kfifo_len(&port->port_write_buf);
if (len < size)
size = len;
if (size != 0)
- size = gs_buf_get(&port->port_write_buf, packet, size);
+ size = kfifo_out(&port->port_write_buf, packet, size);
return size;
}

@@ -398,7 +253,7 @@ __acquires(&port->port_lock)

req->length = len;
list_del(&req->list);
- req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
+ req->zero = kfifo_is_empty(&port->port_write_buf);

pr_vdebug("ttyGS%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
port->port_num, len, *((u8 *)req->buf),
@@ -787,10 +642,11 @@ static int gs_open(struct tty_struct *tty, struct file *file)
spin_lock_irq(&port->port_lock);

/* allocate circular buffer on first open */
- if (port->port_write_buf.buf_buf == NULL) {
+ if (!kfifo_initialized(&port->port_write_buf)) {

spin_unlock_irq(&port->port_lock);
- status = gs_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
+ status = kfifo_alloc(&port->port_write_buf,
+ WRITE_BUF_SIZE, GFP_KERNEL);
spin_lock_irq(&port->port_lock);

if (status) {
@@ -839,7 +695,7 @@ static int gs_writes_finished(struct gs_port *p)

/* return true on disconnect or empty buffer */
spin_lock_irq(&p->port_lock);
- cond = (p->port_usb == NULL) || !gs_buf_data_avail(&p->port_write_buf);
+ cond = (p->port_usb == NULL) || !kfifo_len(&p->port_write_buf);
spin_unlock_irq(&p->port_lock);

return cond;
@@ -875,7 +731,7 @@ static void gs_close(struct tty_struct *tty, struct file *file)
/* wait for circular write buffer to drain, disconnect, or at
* most GS_CLOSE_TIMEOUT seconds; then discard the rest
*/
- if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
+ if (kfifo_len(&port->port_write_buf) > 0 && gser) {
spin_unlock_irq(&port->port_lock);
wait_event_interruptible_timeout(port->drain_wait,
gs_writes_finished(port),
@@ -889,9 +745,9 @@ static void gs_close(struct tty_struct *tty, struct file *file)
* let the push tasklet fire again until we're re-opened.
*/
if (gser == NULL)
- gs_buf_free(&port->port_write_buf);
+ kfifo_free(&port->port_write_buf);
else
- gs_buf_clear(&port->port_write_buf);
+ kfifo_reset(&port->port_write_buf);

port->port.tty = NULL;

@@ -915,7 +771,7 @@ static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)

spin_lock_irqsave(&port->port_lock, flags);
if (count)
- count = gs_buf_put(&port->port_write_buf, buf, count);
+ count = kfifo_in(&port->port_write_buf, buf, count);
/* treat count == 0 as flush_chars() */
if (port->port_usb)
gs_start_tx(port);
@@ -934,7 +790,7 @@ static int gs_put_char(struct tty_struct *tty, unsigned char ch)
port->port_num, tty, ch, __builtin_return_address(0));

spin_lock_irqsave(&port->port_lock, flags);
- status = gs_buf_put(&port->port_write_buf, &ch, 1);
+ status = kfifo_put(&port->port_write_buf, ch);
spin_unlock_irqrestore(&port->port_lock, flags);

return status;
@@ -961,7 +817,7 @@ static int gs_write_room(struct tty_struct *tty)

spin_lock_irqsave(&port->port_lock, flags);
if (port->port_usb)
- room = gs_buf_space_avail(&port->port_write_buf);
+ room = kfifo_avail(&port->port_write_buf);
spin_unlock_irqrestore(&port->port_lock, flags);

pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
@@ -977,7 +833,7 @@ static int gs_chars_in_buffer(struct tty_struct *tty)
int chars = 0;

spin_lock_irqsave(&port->port_lock, flags);
- chars = gs_buf_data_avail(&port->port_write_buf);
+ chars = kfifo_len(&port->port_write_buf);
spin_unlock_irqrestore(&port->port_lock, flags);

pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
@@ -1148,7 +1004,7 @@ static int gs_console_thread(void *data)
ep = port->port_usb->in;

spin_lock_irq(&info->con_lock);
- count = gs_buf_data_avail(&info->con_buf);
+ count = kfifo_len(&info->con_buf);
size = ep->maxpacket;

if (count > 0 && !info->req_busy) {
@@ -1156,7 +1012,7 @@ static int gs_console_thread(void *data)
if (count < size)
size = count;

- xfer = gs_buf_get(&info->con_buf, req->buf, size);
+ xfer = kfifo_out(&info->con_buf, req->buf, size);
req->length = xfer;

spin_unlock(&info->con_lock);
@@ -1192,7 +1048,7 @@ static int gs_console_setup(struct console *co, char *options)
info->req_busy = 0;
spin_lock_init(&info->con_lock);

- status = gs_buf_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE);
+ status = kfifo_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE, GFP_KERNEL);
if (status) {
pr_err("%s: allocate console buffer failed\n", __func__);
return status;
@@ -1202,7 +1058,7 @@ static int gs_console_setup(struct console *co, char *options)
co, "gs_console");
if (IS_ERR(info->console_thread)) {
pr_err("%s: cannot create console thread\n", __func__);
- gs_buf_free(&info->con_buf);
+ kfifo_free(&info->con_buf);
return PTR_ERR(info->console_thread);
}
wake_up_process(info->console_thread);
@@ -1217,7 +1073,7 @@ static void gs_console_write(struct console *co,
unsigned long flags;

spin_lock_irqsave(&info->con_lock, flags);
- gs_buf_put(&info->con_buf, buf, count);
+ kfifo_in(&info->con_buf, buf, count);
spin_unlock_irqrestore(&info->con_lock, flags);

wake_up_process(info->console_thread);
@@ -1256,7 +1112,7 @@ static void gserial_console_exit(void)
unregister_console(&gserial_cons);
if (!IS_ERR_OR_NULL(info->console_thread))
kthread_stop(info->console_thread);
- gs_buf_free(&info->con_buf);
+ kfifo_free(&info->con_buf);
}

#else
@@ -1529,7 +1385,7 @@ void gserial_disconnect(struct gserial *gser)
/* finally, free any unused/unusable I/O buffers */
spin_lock_irqsave(&port->port_lock, flags);
if (port->port.count == 0 && !port->openclose)
- gs_buf_free(&port->port_write_buf);
+ kfifo_free(&port->port_write_buf);
gs_free_requests(gser->out, &port->read_pool, NULL);
gs_free_requests(gser->out, &port->read_queue, NULL);
gs_free_requests(gser->in, &port->write_pool, NULL);
--
2.7.4
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