serial: core: Provide low-level functions to lock port

It will be necessary at times for the uart nbcon console
drivers to acquire the port lock directly (without the
additional nbcon functionality of the port lock wrappers).
These are special cases such as the implementation of the
device_lock()/device_unlock() callbacks or for internal
port lock wrapper synchronization.

Provide low-level variants __uart_port_lock_irqsave() and
__uart_port_unlock_irqrestore() for this purpose.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240820063001.36405-11-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index aea25eef9a1a7b324144c91d9ebbc1045d930a16..8872cd21e70a7d3ba2863651f1729bcadbe33a6c 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -590,6 +590,24 @@ struct uart_port {
        void                    *private_data;          /* generic platform data pointer */
 };
 
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
+{
+       spin_lock_irqsave(&up->lock, *flags);
+}
+
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
+{
+       spin_unlock_irqrestore(&up->lock, flags);
+}
+
 /**
  * uart_port_lock - Lock the UART port
  * @up:                Pointer to UART port structure