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Subject[PATCH v2 2/6] USB: serial: cp210x: fix flow-control error handling
Date
Make sure that the driver crtscts state is not updated in the unlikely
event that the flow-control request fails. Not doing so could break RTS
control.

Fixes: 5951b8508855 ("USB: serial: cp210x: suppress modem-control errors")
Cc: stable@vger.kernel.org # 5.11
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/serial/cp210x.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index fd198031de71..fd6bd574e2a5 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1189,6 +1189,7 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
struct cp210x_flow_ctl flow_ctl;
u32 flow_repl;
u32 ctl_hs;
+ bool crtscts;
int ret;

/*
@@ -1248,14 +1249,14 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;
else
flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
- port_priv->crtscts = true;
+ crtscts = true;
} else {
ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
if (port_priv->rts)
flow_repl |= CP210X_SERIAL_RTS_ACTIVE;
else
flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
- port_priv->crtscts = false;
+ crtscts = false;
}

if (I_IXOFF(tty)) {
@@ -1278,8 +1279,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);

- cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
+ ret = cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
sizeof(flow_ctl));
+ if (ret)
+ goto out_unlock;
+
+ port_priv->crtscts = crtscts;
out_unlock:
mutex_unlock(&port_priv->mutex);
}
--
2.31.1
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