Since the buffer size is a power of 2, we can index into it with
offsets rather than pointers and produce neater code. This
also lets us use every byte in the buffer, rather than having to
reserve one to distinguish empty from free.
---
drivers/usb/gadget/u_serial.c | 58 +++++++++++++++++------------------------
1 files changed, 24 insertions(+), 34 deletions(-)
diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index c44c122..86e9ffc 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -76,13 +76,12 @@
* consider it a NOP. A third layer is provided by the TTY code.
*/
#define QUEUE_SIZE 16
-#define WRITE_BUF_SIZE 8192 /* TX only */
+#define WRITE_BUF_SIZE 8192 /* TX only, must be power of 2 */
/* circular buffer */
struct gs_buf {
- char *buf_buf;
- char *buf_get;
- char *buf_put;
+ char *buf_buf; /* WRITE_BUF_SIZE */
+ unsigned buf_get, buf_put; /* Offsets into buf_buf */
};
/*
@@ -149,8 +148,7 @@ static int gs_buf_alloc(struct gs_buf *gb)
if (gb->buf_buf == NULL)
return -ENOMEM;
- gb->buf_put = gb->buf_buf;
- gb->buf_get = gb->buf_buf;
+ gb->buf_put = gb->buf_get = 0;
return 0;
}
@@ -187,7 +185,7 @@ static void gs_buf_clear(struct gs_buf *gb)
*/
static unsigned gs_buf_data_avail(struct gs_buf const *gb)
{
- return (WRITE_BUF_SIZE + gb->buf_put - gb->buf_get) % WRITE_BUF_SIZE;
+ return gb->buf_put - gb->buf_get;
}
/*
@@ -198,7 +196,7 @@ static unsigned gs_buf_data_avail(struct gs_buf const *gb)
*/
static unsigned gs_buf_space_avail(struct gs_buf const *gb)
{
- return (WRITE_BUF_SIZE + gb->buf_get - gb->buf_put - 1) % WRITE_BUF_SIZE;
+ return WRITE_BUF_SIZE - gs_buf_data_avail(gb);
}
/*
@@ -213,6 +211,7 @@ static unsigned
gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
{
unsigned len;
+ unsigned put_pos = gb->buf_put % WRITE_BUF_SIZE;
len = gs_buf_space_avail(gb);
if (count > len)
@@ -221,18 +220,17 @@ gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
if (count == 0)
return 0;
- len = gb->buf_buf + WRITE_BUF_SIZE - gb->buf_put;
+ len = WRITE_BUF_SIZE - put_pos;
+
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;
+ memcpy(gb->buf_buf + put_pos, buf, len);
+ len = count - len;
+ put_pos = 0;
} else {
- memcpy(gb->buf_put, buf, count);
- if (count < len)
- gb->buf_put += count;
- else /* count == len */
- gb->buf_put = gb->buf_buf;
+ len = count;
}
+ memcpy(gb->buf_buf + put_pos, buf, len);
+ gb->buf_put += count;
return count;
}
@@ -249,6 +247,7 @@ static unsigned
gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
{
unsigned len;
+ unsigned get_pos = gb->buf_get % WRITE_BUF_SIZE;
len = gs_buf_data_avail(gb);
if (count > len)
@@ -257,18 +256,16 @@ gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
if (count == 0)
return 0;
- len = gb->buf_buf + WRITE_BUF_SIZE - gb->buf_get;
+ len = WRITE_BUF_SIZE - get_pos;
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;
+ memcpy(buf, gb->buf_buf + get_pos, len);
+ len = count - len;
+ get_pos = 0;
} else {
- memcpy(buf, gb->buf_get, count);
- if (count < len)
- gb->buf_get += count;
- else /* count == len */
- gb->buf_get = gb->buf_buf;
+ len = count;
}
+ memcpy(buf, gb->buf_buf + get_pos, len);
+ gb->buf_get += count;
return count;
}
@@ -325,14 +322,7 @@ void gs_free_req(struct usb_ep *ep, struct usb_request *req)
static unsigned
gs_send_packet(struct gs_port *port, char *packet, unsigned size)
{
- unsigned len;
-
- len = gs_buf_data_avail(&port->port_write_buf);
- if (len < size)
- size = len;
- if (size != 0)
- size = gs_buf_get(&port->port_write_buf, packet, size);
- return size;
+ return gs_buf_get(&port->port_write_buf, packet, size);
}
/*
--
1.6.3.3
--
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