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tty: add kfifo to tty_port 

Define a kfifo inside struct tty_port. We use DECLARE_KFIFO_PTR and let
the preexisting tty_port::xmit_buf be also the buffer for the kfifo.
And handle the initialization/decomissioning along with xmit_buf, i.e.
in tty_port_alloc_xmit_buf() and tty_port_free_xmit_buf(), respectively.

This allows for kfifo use in drivers which opt-in, while others still
may use the old xmit_buf. mxser will be the first user in the next
few patches.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220124071430.14907-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2022-01-24 08:14:22 +01:00 committed by Greg Kroah-Hartman
parent 702d10a089
commit 4e2a44c140
2 changed files with 8 additions and 1 deletions
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6
drivers/tty/tty_port.c
View File

@ -225,8 +225,11 @@ int tty_port_alloc_xmit_buf(struct tty_port *port)
{
/* We may sleep in get_zeroed_page() */
mutex_lock(&port->buf_mutex);
if (port->xmit_buf == NULL)
if (port->xmit_buf == NULL) {
port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
if (port->xmit_buf)
kfifo_init(&port->xmit_fifo, port->xmit_buf, PAGE_SIZE);
}
mutex_unlock(&port->buf_mutex);
if (port->xmit_buf == NULL)
return -ENOMEM;
@ -240,6 +243,7 @@ void tty_port_free_xmit_buf(struct tty_port *port)
if (port->xmit_buf != NULL) {
free_page((unsigned long)port->xmit_buf);
port->xmit_buf = NULL;
INIT_KFIFO(port->xmit_fifo);
}
mutex_unlock(&port->buf_mutex);
}

3
include/linux/tty_port.h
View File

@ -2,6 +2,7 @@
#ifndef _LINUX_TTY_PORT_H
#define _LINUX_TTY_PORT_H
#include <linux/kfifo.h>
#include <linux/kref.h>
#include <linux/mutex.h>
#include <linux/tty_buffer.h>
@ -67,6 +68,7 @@ extern const struct tty_port_client_operations tty_port_default_client_ops;
* @mutex: locking, for open, shutdown and other port operations
* @buf_mutex: @xmit_buf alloc lock
* @xmit_buf: optional xmit buffer used by some drivers
* @xmit_fifo: optional xmit buffer used by some drivers
* @close_delay: delay in jiffies to wait when closing the port
* @closing_wait: delay in jiffies for output to be sent before closing
* @drain_delay: set to zero if no pure time based drain is needed else set to
@ -110,6 +112,7 @@ struct tty_port {
struct mutex mutex;
struct mutex buf_mutex;
unsigned char *xmit_buf;
DECLARE_KFIFO_PTR(xmit_fifo, unsigned char);
unsigned int close_delay;
unsigned int closing_wait;
int drain_delay;