SSL serial_core.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
*  linux/drivers/char/serial_core.h
*
*  Copyright (C) 2000 Deep Blue Solutions Ltd.
*/
#ifndef LINUX_SERIAL_CORE_H
#define LINUX_SERIAL_CORE_H

#include <linux/bitops.h>
#include <linux/compiler.h>
#include <linux/console.h>
#include <linux/interrupt.h>
#include <linux/lockdep.h>
#include <linux/printk.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/tty.h>
#include <linux/mutex.h>
#include <linux/sysrq.h>
#include <uapi/linux/serial_core.h>

#ifdef CONFIG_SERIAL_CORE_CONSOLE
#define uart_console(port) \
((port)->cons && (port)->cons->index == (port)->line)
#else
#define uart_console(port)      ({ (void)port; 0; })
#endif

struct uart_port;
struct serial_struct;
struct serial_port_device;
struct device;
struct gpio_desc;

/**
* struct uart_ops -- interface between serial_core and the driver
*
* This structure describes all the operations that can be done on the
* physical hardware.
*
* @tx_empty: ``unsigned int ()(struct uart_port *port)``
*
* This function tests whether the transmitter fifo and shifter for the
* @port is empty. If it is empty, this function should return
* %TIOCSER_TEMT, otherwise return 0. If the port does not support this
* operation, then it should return %TIOCSER_TEMT.
*
* Locking: none.
* Interrupts: caller dependent.
* This call must not sleep
*
* @set_mctrl: ``void ()(struct uart_port *port, unsigned int mctrl)``
*
* This function sets the modem control lines for @port to the state
* described by @mctrl. The relevant bits of @mctrl are:
*
* - %TIOCM_RTS RTS signal.
* - %TIOCM_DTR DTR signal.
* - %TIOCM_OUT1 OUT1 signal.
* - %TIOCM_OUT2 OUT2 signal.
* - %TIOCM_LOOP Set the port into loopback mode.
*
* If the appropriate bit is set, the signal should be driven
* active.  If the bit is clear, the signal should be driven
* inactive.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @get_mctrl: ``unsigned int ()(struct uart_port *port)``
*
* Returns the current state of modem control inputs of @port. The state
* of the outputs should not be returned, since the core keeps track of
* their state. The state information should include:
*
* - %TIOCM_CAR state of DCD signal
* - %TIOCM_CTS state of CTS signal
* - %TIOCM_DSR state of DSR signal
* - %TIOCM_RI state of RI signal
*
* The bit is set if the signal is currently driven active.  If
* the port does not support CTS, DCD or DSR, the driver should
* indicate that the signal is permanently active. If RI is
* not available, the signal should not be indicated as active.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @stop_tx: ``void ()(struct uart_port *port)``
*
* Stop transmitting characters. This might be due to the CTS line
* becoming inactive or the tty layer indicating we want to stop
* transmission due to an %XOFF character.
*
* The driver should stop transmitting characters as soon as possible.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @start_tx: ``void ()(struct uart_port *port)``
*
* Start transmitting characters.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @throttle: ``void ()(struct uart_port *port)``
*
* Notify the serial driver that input buffers for the line discipline are
* close to full, and it should somehow signal that no more characters
* should be sent to the serial port.
* This will be called only if hardware assisted flow control is enabled.
*
* Locking: serialized with @unthrottle() and termios modification by the
* tty layer.
*
* @unthrottle: ``void ()(struct uart_port *port)``
*
* Notify the serial driver that characters can now be sent to the serial
* port without fear of overrunning the input buffers of the line
* disciplines.
*
* This will be called only if hardware assisted flow control is enabled.
*
* Locking: serialized with @throttle() and termios modification by the
* tty layer.
*
* @send_xchar: ``void ()(struct uart_port *port, char ch)``
*
* Transmit a high priority character, even if the port is stopped. This
* is used to implement XON/XOFF flow control and tcflow(). If the serial
* driver does not implement this function, the tty core will append the
* character to the circular buffer and then call start_tx() / stop_tx()
* to flush the data out.
*
* Do not transmit if @ch == '\0' (%__DISABLED_CHAR).
*
* Locking: none.
* Interrupts: caller dependent.
*
* @start_rx: ``void ()(struct uart_port *port)``
*
* Start receiving characters.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @stop_rx: ``void ()(struct uart_port *port)``
*
* Stop receiving characters; the @port is in the process of being closed.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @enable_ms: ``void ()(struct uart_port *port)``
*
* Enable the modem status interrupts.
*
* This method may be called multiple times. Modem status interrupts
* should be disabled when the @shutdown() method is called.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @break_ctl: ``void ()(struct uart_port *port, int ctl)``
*
* Control the transmission of a break signal. If @ctl is nonzero, the
* break signal should be transmitted. The signal should be terminated
* when another call is made with a zero @ctl.
*
* Locking: caller holds tty_port->mutex
*
* @startup: ``int ()(struct uart_port *port)``
*
* Grab any interrupt resources and initialise any low level driver state.
* Enable the port for reception. It should not activate RTS nor DTR;
* this will be done via a separate call to @set_mctrl().
*
* This method will only be called when the port is initially opened.
*
* Locking: port_sem taken.
* Interrupts: globally disabled.
*
* @shutdown: ``void ()(struct uart_port *port)``
*
* Disable the @port, disable any break condition that may be in effect,
* and free any interrupt resources. It should not disable RTS nor DTR;
* this will have already been done via a separate call to @set_mctrl().
*
* Drivers must not access @port->state once this call has completed.
*
* This method will only be called when there are no more users of this
* @port.
*
* Locking: port_sem taken.
* Interrupts: caller dependent.
*
* @flush_buffer: ``void ()(struct uart_port *port)``
*
* Flush any write buffers, reset any DMA state and stop any ongoing DMA
* transfers.
*
* This will be called whenever the @port->state->xmit circular buffer is
* cleared.
*
* Locking: @port->lock taken.
* Interrupts: locally disabled.
* This call must not sleep
*
* @set_termios: ``void ()(struct uart_port *port, struct ktermios *new,
* struct ktermios *old)``
*
* Change the @port parameters, including word length, parity, stop bits.
* Update @port->read_status_mask and @port->ignore_status_mask to
* indicate the types of events we are interested in receiving. Relevant
* ktermios::c_cflag bits are:
*
* - %CSIZE - word size
* - %CSTOPB - 2 stop bits
* - %PARENB - parity enable
* - %PARODD - odd parity (when %PARENB is in force)
* - %ADDRB - address bit (changed through uart_port::rs485_config()).
* - %CREAD - enable reception of characters (if not set, still receive
*   characters from the port, but throw them away).
* - %CRTSCTS - if set, enable CTS status change reporting.
* - %CLOCAL - if not set, enable modem status change reporting.
*
* Relevant ktermios::c_iflag bits are:
*
* - %INPCK - enable frame and parity error events to be passed to the TTY
*   layer.
* - %BRKINT / %PARMRK - both of these enable break events to be passed to
*   the TTY layer.
* - %IGNPAR - ignore parity and framing errors.
* - %IGNBRK - ignore break errors. If %IGNPAR is also set, ignore overrun
*   errors as well.
*
* The interaction of the ktermios::c_iflag bits is as follows (parity
* error given as an example):
*
* ============ ======= ======= =========================================
* Parity error INPCK   IGNPAR
* ============ ======= ======= =========================================
* n/a      0      n/a     character received, marked as %TTY_NORMAL
* None      1      n/a     character received, marked as %TTY_NORMAL
* Yes      1      0      character received, marked as %TTY_PARITY
* Yes      1      1      character discarded
* ============ ======= ======= =========================================
*
* Other flags may be used (eg, xon/xoff characters) if your hardware
* supports hardware "soft" flow control.
*
* Locking: caller holds tty_port->mutex
* Interrupts: caller dependent.
* This call must not sleep
*
* @set_ldisc: ``void ()(struct uart_port *port, struct ktermios *termios)``
*
* Notifier for discipline change. See
* Documentation/driver-api/tty/tty_ldisc.rst.
*
* Locking: caller holds tty_port->mutex
*
* @pm: ``void ()(struct uart_port *port, unsigned int state,
* unsigned int oldstate)``
*
* Perform any power management related activities on the specified @port.
* @state indicates the new state (defined by enum uart_pm_state),
* @oldstate indicates the previous state.
*
* This function should not be used to grab any resources.
*
* This will be called when the @port is initially opened and finally
* closed, except when the @port is also the system console. This will
* occur even if %CONFIG_PM is not set.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @type: ``const char *()(struct uart_port *port)``
*
* Return a pointer to a string constant describing the specified @port,
* or return %NULL, in which case the string 'unknown' is substituted.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @release_port: ``void ()(struct uart_port *port)``
*
* Release any memory and IO region resources currently in use by the
* @port.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @request_port: ``int ()(struct uart_port *port)``
*
* Request any memory and IO region resources required by the port. If any
* fail, no resources should be registered when this function returns, and
* it should return -%EBUSY on failure.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @config_port: ``void ()(struct uart_port *port, int type)``
*
* Perform any autoconfiguration steps required for the @port. @type
* contains a bit mask of the required configuration. %UART_CONFIG_TYPE
* indicates that the port requires detection and identification.
* @port->type should be set to the type found, or %PORT_UNKNOWN if no
* port was detected.
*
* %UART_CONFIG_IRQ indicates autoconfiguration of the interrupt signal,
* which should be probed using standard kernel autoprobing techniques.
* This is not necessary on platforms where ports have interrupts
* internally hard wired (eg, system on a chip implementations).
*
* Locking: none.
* Interrupts: caller dependent.
*
* @verify_port: ``int ()(struct uart_port *port,
* struct serial_struct *serinfo)``
*
* Verify the new serial port information contained within @serinfo is
* suitable for this port type.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @ioctl: ``int ()(struct uart_port *port, unsigned int cmd,
* unsigned long arg)``
*
* Perform any port specific IOCTLs. IOCTL commands must be defined using
* the standard numbering system found in <asm/ioctl.h>.
*
* Locking: none.
* Interrupts: caller dependent.
*
* @poll_init: ``int ()(struct uart_port *port)``
*
* Called by kgdb to perform the minimal hardware initialization needed to
* support @poll_put_char() and @poll_get_char(). Unlike @startup(), this
* should not request interrupts.
*
* Locking: %tty_mutex and tty_port->mutex taken.
* Interrupts: n/a.
*
* @poll_put_char: ``void ()(struct uart_port *port, unsigned char ch)``
*
* Called by kgdb to write a single character @ch directly to the serial
* @port. It can and should block until there is space in the TX FIFO.
*
* Locking: none.
* Interrupts: caller dependent.
* This call must not sleep
*
* @poll_get_char: ``int ()(struct uart_port *port)``
*
* Called by kgdb to read a single character directly from the serial
* port. If data is available, it should be returned; otherwise the
* function should return %NO_POLL_CHAR immediately.
*
* Locking: none.
* Interrupts: caller dependent.
* This call must not sleep
*/
struct uart_ops {
unsigned int (*tx_empty)(struct uart_port *);
void  (*set_mctrl)(struct uart_port *, unsigned int mctrl);
unsigned int (*get_mctrl)(struct uart_port *);
void  (*stop_tx)(struct uart_port *);
void  (*start_tx)(struct uart_port *);
void  (*throttle)(struct uart_port *);
void  (*unthrottle)(struct uart_port *);
void  (*send_xchar)(struct uart_port *, char ch);
void  (*stop_rx)(struct uart_port *);
void  (*start_rx)(struct uart_port *);
void  (*enable_ms)(struct uart_port *);
void  (*break_ctl)(struct uart_port *, int ctl);
int  (*startup)(struct uart_port *);
void  (*shutdown)(struct uart_port *);
void  (*flush_buffer)(struct uart_port *);
void  (*set_termios)(struct uart_port *, struct ktermios *new,
           const struct ktermios *old);
void  (*set_ldisc)(struct uart_port *, struct ktermios *);
void  (*pm)(struct uart_port *, unsigned int state,
         unsigned int oldstate);
const char *(*type)(struct uart_port *);
void  (*release_port)(struct uart_port *);
int  (*request_port)(struct uart_port *);
void  (*config_port)(struct uart_port *, int);
int  (*verify_port)(struct uart_port *, struct serial_struct *);
int  (*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLL
int  (*poll_init)(struct uart_port *);
void  (*poll_put_char)(struct uart_port *, unsigned char);
int  (*poll_get_char)(struct uart_port *);
#endif
};

#define NO_POLL_CHAR  0x00ff0000
#define UART_CONFIG_TYPE (1 << 0)
#define UART_CONFIG_IRQ  (1 << 1)

struct uart_icount {
__u32 cts;
__u32 dsr;
__u32 rng;
__u32 dcd;
__u32 rx;
__u32 tx;
__u32 frame;
__u32 overrun;
__u32 parity;
__u32 brk;
__u32 buf_overrun;
};

typedef u64 __bitwise upf_t;
typedef unsigned int __bitwise upstat_t;

enum uart_iotype {
UPIO_UNKNOWN = -1,
UPIO_PORT = SERIAL_IO_PORT, /* 8b I/O port access */
UPIO_HUB6 = SERIAL_IO_HUB6, /* Hub6 ISA card */
UPIO_MEM = SERIAL_IO_MEM, /* driver-specific */
UPIO_MEM32 = SERIAL_IO_MEM32, /* 32b little endian */
UPIO_AU  = SERIAL_IO_AU,  /* Au1x00 and RT288x type IO */
UPIO_TSI = SERIAL_IO_TSI, /* Tsi108/109 type IO */
UPIO_MEM32BE = SERIAL_IO_MEM32BE, /* 32b big endian */
UPIO_MEM16 = SERIAL_IO_MEM16, /* 16b little endian */
};

struct uart_port {
spinlock_t  lock;   /* port lock */
unsigned long  iobase;   /* in/out[bwl] */
unsigned char __iomem *membase;  /* read/write[bwl] */
u32   (*serial_in)(struct uart_port *, unsigned int offset);
void   (*serial_out)(struct uart_port *, unsigned int offset, u32 val);
void   (*set_termios)(struct uart_port *,
                   struct ktermios *new,
                   const struct ktermios *old);
void   (*set_ldisc)(struct uart_port *,
          struct ktermios *);
unsigned int  (*get_mctrl)(struct uart_port *);
void   (*set_mctrl)(struct uart_port *, unsigned int);
unsigned int  (*get_divisor)(struct uart_port *,
            unsigned int baud,
            unsigned int *frac);
void   (*set_divisor)(struct uart_port *,
            unsigned int baud,
            unsigned int quot,
            unsigned int quot_frac);
int   (*startup)(struct uart_port *port);
void   (*shutdown)(struct uart_port *port);
void   (*throttle)(struct uart_port *port);
void   (*unthrottle)(struct uart_port *port);
int   (*handle_irq)(struct uart_port *);
void   (*pm)(struct uart_port *, unsigned int state,
          unsigned int old);
void   (*handle_break)(struct uart_port *);
int   (*rs485_config)(struct uart_port *,
      struct ktermios *termios,
      struct serial_rs485 *rs485);
int   (*iso7816_config)(struct uart_port *,
        struct serial_iso7816 *iso7816);
unsigned int  ctrl_id;  /* optional serial core controller id */
unsigned int  port_id;  /* optional serial core port id */
unsigned int  irq;   /* irq number */
unsigned long  irqflags;  /* irq flags  */
unsigned int  uartclk;  /* base uart clock */
unsigned int  fifosize;  /* tx fifo size */
unsigned char  x_char;   /* xon/xoff char */
unsigned char  regshift;  /* reg offset shift */

unsigned char  quirks;   /* internal quirks */

/* internal quirks must be updated while holding port mutex */
#define UPQ_NO_TXEN_TEST BIT(0)

enum uart_iotype iotype;   /* io access style */

unsigned int  read_status_mask; /* driver specific */
unsigned int  ignore_status_mask; /* driver specific */
struct uart_state *state;   /* pointer to parent state */
struct uart_icount icount;   /* statistics */

struct console  *cons;   /* struct console, if any */
/* flags must be updated while holding port mutex */
upf_t   flags;

/*
* These flags must be equivalent to the flags defined in
* include/uapi/linux/tty_flags.h which are the userspace definitions
* assigned from the serial_struct flags in uart_set_info()
* [for bit definitions in the UPF_CHANGE_MASK]
*
* Bits [0..ASYNCB_LAST_USER] are userspace defined/visible/changeable
* The remaining bits are serial-core specific and not modifiable by
* userspace.
*/
#ifdef CONFIG_HAS_IOPORT
#define UPF_FOURPORT  ((__force upf_t) ASYNC_FOURPORT       /* 1  */ )
#else
#define UPF_FOURPORT  0
#endif
#define UPF_SAK   ((__force upf_t) ASYNC_SAK            /* 2  */ )
#define UPF_SPD_HI  ((__force upf_t) ASYNC_SPD_HI         /* 4  */ )
#define UPF_SPD_VHI  ((__force upf_t) ASYNC_SPD_VHI        /* 5  */ )
#define UPF_SPD_CUST  ((__force upf_t) ASYNC_SPD_CUST   /* 0x0030 */ )
#define UPF_SPD_WARP  ((__force upf_t) ASYNC_SPD_WARP   /* 0x1010 */ )
#define UPF_SPD_MASK  ((__force upf_t) ASYNC_SPD_MASK   /* 0x1030 */ )
#define UPF_SKIP_TEST  ((__force upf_t) ASYNC_SKIP_TEST      /* 6  */ )
#define UPF_AUTO_IRQ  ((__force upf_t) ASYNC_AUTO_IRQ       /* 7  */ )
#define UPF_HARDPPS_CD  ((__force upf_t) ASYNC_HARDPPS_CD     /* 11 */ )
#define UPF_SPD_SHI  ((__force upf_t) ASYNC_SPD_SHI        /* 12 */ )
#define UPF_LOW_LATENCY  ((__force upf_t) ASYNC_LOW_LATENCY    /* 13 */ )
#define UPF_BUGGY_UART  ((__force upf_t) ASYNC_BUGGY_UART     /* 14 */ )
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )

#define UPF_NO_THRE_TEST ((__force upf_t) BIT_ULL(19))
/* Port has hardware-assisted h/w flow control */
#define UPF_AUTO_CTS  ((__force upf_t) BIT_ULL(20))
#define UPF_AUTO_RTS  ((__force upf_t) BIT_ULL(21))
#define UPF_HARD_FLOW  ((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS))
/* Port has hardware-assisted s/w flow control */
#define UPF_SOFT_FLOW  ((__force upf_t) BIT_ULL(22))
#define UPF_CONS_FLOW  ((__force upf_t) BIT_ULL(23))
#define UPF_SHARE_IRQ  ((__force upf_t) BIT_ULL(24))
#define UPF_EXAR_EFR  ((__force upf_t) BIT_ULL(25))
#define UPF_BUG_THRE  ((__force upf_t) BIT_ULL(26))
/* The exact UART type is known and should not be probed.  */
#define UPF_FIXED_TYPE  ((__force upf_t) BIT_ULL(27))
#define UPF_BOOT_AUTOCONF ((__force upf_t) BIT_ULL(28))
#define UPF_FIXED_PORT  ((__force upf_t) BIT_ULL(29))
#define UPF_DEAD  ((__force upf_t) BIT_ULL(30))
#define UPF_IOREMAP  ((__force upf_t) BIT_ULL(31))
#define UPF_FULL_PROBE  ((__force upf_t) BIT_ULL(32))

#define __UPF_CHANGE_MASK 0x17fff
#define UPF_CHANGE_MASK  ((__force upf_t) __UPF_CHANGE_MASK)
#define UPF_USR_MASK  ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

#if __UPF_CHANGE_MASK > ASYNC_FLAGS
#error Change mask not equivalent to userspace-visible bit defines
#endif

/*
* Must hold termios_rwsem, port mutex and port lock to change;
* can hold any one lock to read.
*/
upstat_t  status;

#define UPSTAT_CTS_ENABLE ((__force upstat_t) (1 << 0))
#define UPSTAT_DCD_ENABLE ((__force upstat_t) (1 << 1))
#define UPSTAT_AUTORTS  ((__force upstat_t) (1 << 2))
#define UPSTAT_AUTOCTS  ((__force upstat_t) (1 << 3))
#define UPSTAT_AUTOXOFF  ((__force upstat_t) (1 << 4))
#define UPSTAT_SYNC_FIFO ((__force upstat_t) (1 << 5))

bool   hw_stopped;  /* sw-assisted CTS flow state */
unsigned int  mctrl;   /* current modem ctrl settings */
unsigned int  frame_time;  /* frame timing in ns */
unsigned int  type;   /* port type */
const struct uart_ops *ops;
unsigned int  custom_divisor;
unsigned int  line;   /* port index */
unsigned int  minor;
resource_size_t  mapbase;  /* for ioremap */
resource_size_t  mapsize;
struct device  *dev;   /* serial port physical parent device */
struct serial_port_device *port_dev;  /* serial core port device */

unsigned long  sysrq;   /* sysrq timeout */
u8   sysrq_ch;  /* char for sysrq */
unsigned char  has_sysrq;
unsigned char  sysrq_seq;  /* index in sysrq_toggle_seq */

unsigned char  hub6;   /* this should be in the 8250 driver */
unsigned char  suspended;
unsigned char  console_reinit;
const char  *name;   /* port name */
struct attribute_group *attr_group;  /* port specific attributes */
const struct attribute_group **tty_groups; /* all attributes (serial core use only) */
struct serial_rs485     rs485;
struct serial_rs485 rs485_supported; /* Supported mask for serial_rs485 */
struct gpio_desc *rs485_term_gpio; /* enable RS485 bus termination */
struct gpio_desc *rs485_rx_during_tx_gpio; /* Output GPIO that sets the state of RS485 RX during TX */
struct serial_iso7816   iso7816;
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_set_cons - Safely set the @cons field for a uart
* @up: The uart port to set
* @con: The new console to set to
*
* This function must be used to set @up->cons. It uses the port lock to
* synchronize with the port lock wrappers in order to ensure that the console
* cannot change or disappear while another context is holding the port lock.
*/
static inline void uart_port_set_cons(struct uart_port *up, struct console *con)
{
unsigned long flags;

__uart_port_lock_irqsave(up, &flags);
up->cons = con;
__uart_port_unlock_irqrestore(up, flags);
}

/* Only for internal port lock wrapper usage. */
static inline bool __uart_port_using_nbcon(struct uart_port *up)
{
lockdep_assert_held_once(&up->lock);

if (likely(!uart_console(up)))
  return false;

/*
* @up->cons is only modified under the port lock. Therefore it is
* certain that it cannot disappear here.
*
* @up->cons->node is added/removed from the console list under the
* port lock. Therefore it is certain that the registration status
* cannot change here, thus @up->cons->flags can be read directly.
*/
if (hlist_unhashed_lockless(&up->cons->node) ||
     !(up->cons->flags & CON_NBCON) ||
     !up->cons->write_atomic) {
  return false;
}

return true;
}

/* Only for internal port lock wrapper usage. */
static inline bool __uart_port_nbcon_try_acquire(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
  return true;

return nbcon_device_try_acquire(up->cons);
}

/* Only for internal port lock wrapper usage. */
static inline void __uart_port_nbcon_acquire(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
  return;

while (!nbcon_device_try_acquire(up->cons))
  cpu_relax();
}

/* Only for internal port lock wrapper usage. */
static inline void __uart_port_nbcon_release(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
  return;

nbcon_device_release(up->cons);
}

/**
* uart_port_lock - Lock the UART port
* @up: Pointer to UART port structure
*/
static inline void uart_port_lock(struct uart_port *up)
{
spin_lock(&up->lock);
__uart_port_nbcon_acquire(up);
}

/**
* uart_port_lock_irq - Lock the UART port and disable interrupts
* @up: Pointer to UART port structure
*/
static inline void uart_port_lock_irq(struct uart_port *up)
{
spin_lock_irq(&up->lock);
__uart_port_nbcon_acquire(up);
}

/**
* uart_port_lock_irqsave - Lock the UART port, save and disable interrupts
* @up: Pointer to UART port structure
* @flags: Pointer to interrupt flags storage
*/
static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
{
spin_lock_irqsave(&up->lock, *flags);
__uart_port_nbcon_acquire(up);
}

/**
* uart_port_trylock - Try to lock the UART port
* @up: Pointer to UART port structure
*
* Returns: True if lock was acquired, false otherwise
*/
static inline bool uart_port_trylock(struct uart_port *up)
{
if (!spin_trylock(&up->lock))
  return false;

if (!__uart_port_nbcon_try_acquire(up)) {
  spin_unlock(&up->lock);
  return false;
}

return true;
}

/**
* uart_port_trylock_irqsave - Try to lock the UART port, save and disable interrupts
* @up: Pointer to UART port structure
* @flags: Pointer to interrupt flags storage
*
* Returns: True if lock was acquired, false otherwise
*/
static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long *flags)
{
if (!spin_trylock_irqsave(&up->lock, *flags))
  return false;

if (!__uart_port_nbcon_try_acquire(up)) {
  spin_unlock_irqrestore(&up->lock, *flags);
  return false;
}

return true;
}

/**
* uart_port_unlock - Unlock the UART port
* @up: Pointer to UART port structure
*/
static inline void uart_port_unlock(struct uart_port *up)
{
__uart_port_nbcon_release(up);
spin_unlock(&up->lock);
}

/**
* uart_port_unlock_irq - Unlock the UART port and re-enable interrupts
* @up: Pointer to UART port structure
*/
static inline void uart_port_unlock_irq(struct uart_port *up)
{
__uart_port_nbcon_release(up);
spin_unlock_irq(&up->lock);
}

/**
* uart_port_unlock_irqrestore - Unlock the UART port, restore interrupts
* @up: Pointer to UART port structure
* @flags: The saved interrupt flags for restore
*/
static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
{
__uart_port_nbcon_release(up);
spin_unlock_irqrestore(&up->lock, flags);
}

static inline int serial_port_in(struct uart_port *up, int offset)
{
return up->serial_in(up, offset);
}

static inline void serial_port_out(struct uart_port *up, int offset, int value)
{
up->serial_out(up, offset, value);
}

/**
* enum uart_pm_state - power states for UARTs
* @UART_PM_STATE_ON: UART is powered, up and operational
* @UART_PM_STATE_OFF: UART is powered off
* @UART_PM_STATE_UNDEFINED: sentinel
*/
enum uart_pm_state {
UART_PM_STATE_ON = 0,
UART_PM_STATE_OFF = 3, /* number taken from ACPI */
UART_PM_STATE_UNDEFINED,
};

/*
* This is the state information which is persistent across opens.
*/
struct uart_state {
struct tty_port  port;

enum uart_pm_state pm_state;

atomic_t  refcount;
wait_queue_head_t remove_wait;
struct uart_port *uart_port;
};

#define UART_XMIT_SIZE PAGE_SIZE

/* 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 tty_port *tport = &up->state->port;

kfifo_skip_count(&tport->xmit_fifo, chars);
up->icount.tx += chars;
}

static inline unsigned int uart_fifo_out(struct uart_port *up,
  unsigned char *buf, unsigned int chars)
{
struct tty_port *tport = &up->state->port;

chars = kfifo_out(&tport->xmit_fifo, buf, chars);
up->icount.tx += chars;

return chars;
}

static inline unsigned int uart_fifo_get(struct uart_port *up,
  unsigned char *ch)
{
struct tty_port *tport = &up->state->port;
unsigned int chars;

chars = kfifo_get(&tport->xmit_fifo, ch);
up->icount.tx += chars;

return chars;
}

struct module;
struct tty_driver;

struct uart_driver {
struct module  *owner;
const char  *driver_name;
const char  *dev_name;
int    major;
int    minor;
int    nr;
struct console  *cons;

/*
* these are private; the low level driver should not
* touch these; they should be initialised to NULL
*/
struct uart_state *state;
struct tty_driver *tty_driver;
};

void uart_write_wakeup(struct uart_port *port);

/**
* enum UART_TX_FLAGS -- flags for uart_port_tx_flags()
*
* @UART_TX_NOSTOP: don't call port->ops->stop_tx() on empty buffer
*/
enum UART_TX_FLAGS {
UART_TX_NOSTOP = BIT(0),
};

#define __uart_port_tx(uport, ch, flags, tx_ready, put_char, tx_done,       \
         for_test, for_post)          \
({               \
struct uart_port *__port = (uport);          \
struct tty_port *__tport = &__port->state->port;        \
unsigned int pending;            \
               \
for (; (for_test) && (tx_ready); (for_post), __port->icount.tx++) {   \
  if (__port->x_char) {           \
   (ch) = __port->x_char;          \
   (put_char);           \
   __port->x_char = 0;          \
   continue;           \
  }             \
               \
  if (uart_tx_stopped(__port))          \
   break;            \
               \
  if (!kfifo_get(&__tport->xmit_fifo, &(ch)))        \
   break;            \
               \
  (put_char);            \
}              \
               \
(tx_done);             \
               \
pending = kfifo_len(&__tport->xmit_fifo);         \
if (pending < WAKEUP_CHARS) {           \
  uart_write_wakeup(__port);          \
               \
  if (!((flags) & UART_TX_NOSTOP) && pending == 0)       \
   __port->ops->stop_tx(__port);         \
}              \
               \
pending;             \
})

/**
* uart_port_tx_limited -- transmit helper for uart_port with count limiting
* @port: uart port
* @ch: variable to store a character to be written to the HW
* @count: a limit of characters to send
* @tx_ready: can HW accept more data function
* @put_char: function to write a character
* @tx_done: function to call after the loop is done
*
* This helper transmits characters from the xmit buffer to the hardware using
* @put_char(). It does so until @count characters are sent and while @tx_ready
* evaluates to true.
*
* Returns: the number of characters in the xmit buffer when done.
*
* The expression in macro parameters shall be designed as follows:
*  * **tx_ready:** should evaluate to true if the HW can accept more data to
*    be sent. This parameter can be %true, which means the HW is always ready.
*  * **put_char:** shall write @ch to the device of @port.
*  * **tx_done:** when the write loop is done, this can perform arbitrary
*    action before potential invocation of ops->stop_tx() happens. If the
*    driver does not need to do anything, use e.g. ({}).
*
* For all of them, @port->lock is held, interrupts are locally disabled and
* the expressions must not sleep.
*/
#define uart_port_tx_limited(port, ch, count, tx_ready, put_char, tx_done) ({ \
unsigned int __count = (count);           \
__uart_port_tx(port, ch, 0, tx_ready, put_char, tx_done, __count,     \
   __count--);           \
})

/**
* uart_port_tx_limited_flags -- transmit helper for uart_port with count limiting with flags
* @port: uart port
* @ch: variable to store a character to be written to the HW
* @flags: %UART_TX_NOSTOP or similar
* @count: a limit of characters to send
* @tx_ready: can HW accept more data function
* @put_char: function to write a character
* @tx_done: function to call after the loop is done
*
* See uart_port_tx_limited() for more details.
*/
#define uart_port_tx_limited_flags(port, ch, flags, count, tx_ready, put_char, tx_done) ({ \
unsigned int __count = (count);          \
__uart_port_tx(port, ch, flags, tx_ready, put_char, tx_done, __count,     \
   __count--);          \
})

/**
* uart_port_tx -- transmit helper for uart_port
* @port: uart port
* @ch: variable to store a character to be written to the HW
* @tx_ready: can HW accept more data function
* @put_char: function to write a character
*
* See uart_port_tx_limited() for more details.
*/
#define uart_port_tx(port, ch, tx_ready, put_char)   \
__uart_port_tx(port, ch, 0, tx_ready, put_char, ({}), true, ({}))

/**
* uart_port_tx_flags -- transmit helper for uart_port with flags
* @port: uart port
* @ch: variable to store a character to be written to the HW
* @flags: %UART_TX_NOSTOP or similar
* @tx_ready: can HW accept more data function
* @put_char: function to write a character
*
* See uart_port_tx_limited() for more details.
*/
#define uart_port_tx_flags(port, ch, flags, tx_ready, put_char)  \
__uart_port_tx(port, ch, flags, tx_ready, put_char, ({}), true, ({}))
/*
* Baud rate helpers.
*/
void uart_update_timeout(struct uart_port *port, unsigned int cflag,
    unsigned int baud);
unsigned int uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
    const struct ktermios *old, unsigned int min,
    unsigned int max);
unsigned int uart_get_divisor(struct uart_port *port, unsigned int baud);

/*
* Calculates FIFO drain time.
*/
static inline unsigned long uart_fifo_timeout(struct uart_port *port)
{
u64 fifo_timeout = (u64)READ_ONCE(port->frame_time) * port->fifosize;

/* Add .02 seconds of slop */
fifo_timeout += 20 * NSEC_PER_MSEC;

return max(nsecs_to_jiffies(fifo_timeout), 1UL);
}

/* Base timer interval for polling */
static inline unsigned long uart_poll_timeout(struct uart_port *port)
{
unsigned long timeout = uart_fifo_timeout(port);

return timeout > 6 ? (timeout / 2 - 2) : 1;
}

/*
* Console helpers.
*/
struct earlycon_device {
struct console *con;
struct uart_port port;
char options[32];  /* e.g., 115200n8 */
unsigned int baud;
};

struct earlycon_id {
char name[15];
char name_term; /* In case compiler didn't '\0' term name */
char compatible[128];
int (*setup)(struct earlycon_device *, const char *options);
};

extern const struct earlycon_id __earlycon_table[];
extern const struct earlycon_id __earlycon_table_end[];

#if defined(CONFIG_SERIAL_EARLYCON) && !defined(MODULE)
#define EARLYCON_USED_OR_UNUSED __used
#else
#define EARLYCON_USED_OR_UNUSED __maybe_unused
#endif

#define OF_EARLYCON_DECLARE(_name, compat, fn)    \
static const struct earlycon_id __UNIQUE_ID(__earlycon_##_name) \
  EARLYCON_USED_OR_UNUSED  __section("__earlycon_table")  \
  __aligned(__alignof__(struct earlycon_id))  \
  = { .name = __stringify(_name),    \
      .compatible = compat,    \
      .setup = fn }

#define EARLYCON_DECLARE(_name, fn) OF_EARLYCON_DECLARE(_name, "", fn)

int of_setup_earlycon(const struct earlycon_id *match, unsigned long node,
        const char *options);

#ifdef CONFIG_SERIAL_EARLYCON
extern bool earlycon_acpi_spcr_enable __initdata;
int setup_earlycon(char *buf);
#else
static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED;
static inline int setup_earlycon(char *buf) { return 0; }
#endif

/* Variant of uart_console_registered() when the console_list_lock is held. */
static inline bool uart_console_registered_locked(struct uart_port *port)
{
return uart_console(port) && console_is_registered_locked(port->cons);
}

static inline bool uart_console_registered(struct uart_port *port)
{
return uart_console(port) && console_is_registered(port->cons);
}

int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
   resource_size_t *addr, char **options);
void uart_parse_options(const char *options, int *baud, int *parity, int *bits,
   int *flow);
int uart_set_options(struct uart_port *port, struct console *co, int baud,
       int parity, int bits, int flow);
struct tty_driver *uart_console_device(struct console *co, int *index);
void uart_console_write(struct uart_port *port, const char *s,
   unsigned int count,
   void (*putchar)(struct uart_port *, unsigned char));

/*
* Port/driver registration/removal
*/
int uart_register_driver(struct uart_driver *uart);
void uart_unregister_driver(struct uart_driver *uart);
int uart_add_one_port(struct uart_driver *reg, struct uart_port *port);
void uart_remove_one_port(struct uart_driver *reg, struct uart_port *port);
int uart_read_port_properties(struct uart_port *port);
int uart_read_and_validate_port_properties(struct uart_port *port);
bool uart_match_port(const struct uart_port *port1,
  const struct uart_port *port2);

/*
* Power Management
*/
int uart_suspend_port(struct uart_driver *reg, struct uart_port *port);
int uart_resume_port(struct uart_driver *reg, struct uart_port *port);

static inline int uart_tx_stopped(struct uart_port *port)
{
struct tty_struct *tty = port->state->port.tty;
if ((tty && tty->flow.stopped) || port->hw_stopped)
  return 1;
return 0;
}

static inline bool uart_cts_enabled(struct uart_port *uport)
{
return !!(uport->status & UPSTAT_CTS_ENABLE);
}

static inline bool uart_softcts_mode(struct uart_port *uport)
{
upstat_t mask = UPSTAT_CTS_ENABLE | UPSTAT_AUTOCTS;

return ((uport->status & mask) == UPSTAT_CTS_ENABLE);
}

/*
* The following are helper functions for the low level drivers.
*/

void uart_handle_dcd_change(struct uart_port *uport, bool active);
void uart_handle_cts_change(struct uart_port *uport, bool active);

void uart_insert_char(struct uart_port *port, unsigned int status,
        unsigned int overrun, u8 ch, u8 flag);

void uart_xchar_out(struct uart_port *uport, int offset);

#ifdef CONFIG_MAGIC_SYSRQ_SERIAL
#define SYSRQ_TIMEOUT (HZ * 5)

bool uart_try_toggle_sysrq(struct uart_port *port, u8 ch);

static inline int uart_handle_sysrq_char(struct uart_port *port, u8 ch)
{
if (!port->sysrq)
  return 0;

if (ch && time_before(jiffies, port->sysrq)) {
  if (sysrq_mask()) {
   handle_sysrq(ch);
   port->sysrq = 0;
   return 1;
  }
  if (uart_try_toggle_sysrq(port, ch))
   return 1;
}
port->sysrq = 0;

return 0;
}

static inline int uart_prepare_sysrq_char(struct uart_port *port, u8 ch)
{
if (!port->sysrq)
  return 0;

if (ch && time_before(jiffies, port->sysrq)) {
  if (sysrq_mask()) {
   port->sysrq_ch = ch;
   port->sysrq = 0;
   return 1;
  }
  if (uart_try_toggle_sysrq(port, ch))
   return 1;
}
port->sysrq = 0;

return 0;
}

static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
{
u8 sysrq_ch;

if (!port->has_sysrq) {
  uart_port_unlock(port);
  return;
}

sysrq_ch = port->sysrq_ch;
port->sysrq_ch = 0;

uart_port_unlock(port);

if (sysrq_ch)
  handle_sysrq(sysrq_ch);
}

static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
  unsigned long flags)
{
u8 sysrq_ch;

if (!port->has_sysrq) {
  uart_port_unlock_irqrestore(port, flags);
  return;
}

sysrq_ch = port->sysrq_ch;
port->sysrq_ch = 0;

uart_port_unlock_irqrestore(port, flags);

if (sysrq_ch)
  handle_sysrq(sysrq_ch);
}
#else /* CONFIG_MAGIC_SYSRQ_SERIAL */
static inline int uart_handle_sysrq_char(struct uart_port *port, u8 ch)
{
return 0;
}
static inline int uart_prepare_sysrq_char(struct uart_port *port, u8 ch)
{
return 0;
}
static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
{
uart_port_unlock(port);
}
static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
  unsigned long flags)
{
uart_port_unlock_irqrestore(port, flags);
}
#endif /* CONFIG_MAGIC_SYSRQ_SERIAL */

/*
* We do the SysRQ and SAK checking like this...
*/
static inline int uart_handle_break(struct uart_port *port)
{
struct uart_state *state = port->state;

if (port->handle_break)
  port->handle_break(port);

#ifdef CONFIG_MAGIC_SYSRQ_SERIAL
if (port->has_sysrq && uart_console(port)) {
  if (!port->sysrq) {
   port->sysrq = jiffies + SYSRQ_TIMEOUT;
   return 1;
  }
  port->sysrq = 0;
}
#endif
if (port->flags & UPF_SAK)
  do_SAK(state->port.tty);
return 0;
}

/*
* UART_ENABLE_MS - determine if port should enable modem status irqs
*/
#define UART_ENABLE_MS(port,cflag) ((port)->flags & UPF_HARDPPS_CD || \
      (cflag) & CRTSCTS || \
      !((cflag) & CLOCAL))

int uart_get_rs485_mode(struct uart_port *port);
#endif /* LINUX_SERIAL_CORE_H */

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