TononixOS/ubports_kernel_google_msm
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msm: tty: update receive room just before writing data to the ldisc

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There is a corner case in the tty driver where the value of
tty->receive_room is not being updated before writing data to
the line discipline. When this happens, data is lost because
of failure to re-submit any remaining data to the ldisc.

This fix is dependent on a new tty flag that is set only when
the tty driver is used for efs sync betweem the mdm modem and
the applications processor.

CRs-Fixed: 358868
Change-Id: I0ba02980504b4d8187b8c83111c2c883d194efa2
Signed-off-by: Joel King <joelking@codeaurora.org>
This commit is contained in:
Joel King
2012-07-11 16:18:54 -07:00
committed by Stephen Boyd
parent 8b6e5d26eb
commit aa1f4fe003
3 changed files with 30 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/tty/tty_buffer.c
View File

@@ -418,6 +418,8 @@ static void flush_to_ldisc(struct work_struct *work)
int count;
char *char_buf;
unsigned char *flag_buf;
unsigned int left = 0;
unsigned int max_space;
count = head->commit - head->read;
if (!count) {
@@ -432,10 +434,33 @@ static void flush_to_ldisc(struct work_struct *work)
line discipline as we want to empty the queue */
if (test_bit(TTY_FLUSHPENDING, &tty->flags))
break;
/* update receive room */
spin_lock(&tty->read_lock);
if (tty->update_room_in_ldisc) {
if ((tty->read_cnt == N_TTY_BUF_SIZE - 1) &&
(tty->receive_room ==
N_TTY_BUF_SIZE - 1))
tty->rr_bug++;
left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
}
spin_unlock(&tty->read_lock);
if (!tty->receive_room)
break;
if (count > tty->receive_room)
count = tty->receive_room;
if (tty->update_room_in_ldisc && !left) {
schedule_work(&tty->buf.work);
break;
}
if (tty->update_room_in_ldisc)
max_space = min(left, tty->receive_room);
else
max_space = tty->receive_room;
if (count > max_space)
count = max_space;
char_buf = head->char_buf_ptr + head->read;
flag_buf = head->flag_buf_ptr + head->read;
head->read += count;

1
drivers/usb/serial/usb_wwan.c
View File

@@ -495,6 +495,7 @@ int usb_wwan_open(struct tty_struct *tty, struct usb_serial_port *port)
/* explicitly set the driver mode to raw */
tty->raw = 1;
tty->real_raw = 1;
tty->update_room_in_ldisc = 1;
set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
dbg("%s", __func__);

2
include/linux/tty.h
View File

@@ -282,8 +282,10 @@ struct tty_struct {
struct winsize winsize; /* termios mutex */
unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
unsigned char low_latency:1, warned:1;
unsigned char update_room_in_ldisc:1;
unsigned char ctrl_status; /* ctrl_lock */
unsigned int receive_room; /* Bytes free for queue */
unsigned int rr_bug;
struct tty_struct *link;
struct fasync_struct *fasync;