[PATCH 5.15 119/148] serial: Create uart_xmit_advance()

Greg Kroah-Hartman
2022-09-26T11:27:24Z

From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

commit e77cab77f2cb3a1ca2ba8df4af45bb35617ac16d upstream.

A very common pattern in the drivers is to advance xmit tail
index and do bookkeeping of Tx'ed characters. Create
uart_xmit_advance() to handle it.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220901143934.8850-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/serial_core.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -300,6 +300,23 @@ struct uart_state {
/* number of characters left in xmit buffer before we ask for more */
#define WAKEUP_CHARS 256

+/**
+ * uart_xmit_advance - Advance xmit buffer and account Tx'ed chars
+ * @up: uart_port structure describing the port
+ * @chars: number of characters sent
+ *
+ * This function advances the tail of circular xmit buffer by the number of
+ * @chars transmitted and handles accounting of transmitted bytes (into
+ * @up's icount.tx).
+ */
+static inline void uart_xmit_advance(struct uart_port *up, unsigned int chars)
+{
+ struct circ_buf *xmit = &up->state->xmit;
+
+ xmit->tail = (xmit->tail + chars) & (UART_XMIT_SIZE - 1);
+ up->icount.tx += chars;
+}
+
struct module;
struct tty_driver;