// SPDX-License-Identifier: GPL-2.0 /* * Tty port functions */ #include <linux/types.h> #include <linux/errno.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/tty_flip.h> #include <linux/serial.h> #include <linux/timer.h> #include <linux/string.h> #include <linux/slab.h> #include <linux/sched/signal.h> #include <linux/wait.h> #include <linux/bitops.h> #include <linux/delay.h> #include <linux/module.h> #include <linux/serdev.h> #include "tty.h" static size_t tty_port_default_receive_buf(struct tty_port *port, const u8 *p, const u8 *f, size_t count) { struct tty_struct *tty; struct tty_ldisc *ld; tty = READ_ONCE(port->itty); if (!tty) return 0; ld = tty_ldisc_ref(tty); if (!ld) return 0; count = tty_ldisc_receive_buf(ld, p, f, count); tty_ldisc_deref(ld); return count; } static void tty_port_default_lookahead_buf(struct tty_port *port, const u8 *p, const u8 *f, size_t count) { struct tty_struct *tty; struct tty_ldisc *ld; tty = READ_ONCE(port->itty); if (!tty) return; ld = tty_ldisc_ref(tty); if (!ld) return; if (ld->ops->lookahead_buf) ld->ops->lookahead_buf(ld->tty, p, f, count); tty_ldisc_deref(ld); } static void tty_port_default_wakeup(struct tty_port *port) { struct tty_struct *tty = tty_port_tty_get(port); if (tty) { tty_wakeup(tty); tty_kref_put(tty); } } const struct tty_port_client_operations tty_port_default_client_ops = { .receive_buf = tty_port_default_receive_buf, .lookahead_buf = tty_port_default_lookahead_buf, .write_wakeup = tty_port_default_wakeup, }; EXPORT_SYMBOL_GPL(tty_port_default_client_ops); /** * tty_port_init -- initialize tty_port * @port: tty_port to initialize * * Initializes the state of struct tty_port. When a port was initialized using * this function, one has to destroy the port by tty_port_destroy(). Either * indirectly by using &tty_port refcounting (tty_port_put()) or directly if * refcounting is not used. */ void tty_port_init(struct tty_port *port) { memset(port, 0, sizeof(*port)); tty_buffer_init(port); init_waitqueue_head(&port->open_wait); init_waitqueue_head(&port->delta_msr_wait); mutex_init(&port->mutex); mutex_init(&port->buf_mutex); spin_lock_init(&port->lock); port->close_delay = (50 * HZ) / 100; port->closing_wait = (3000 * HZ) / 100; port->client_ops = &tty_port_default_client_ops; kref_init(&port->kref); } EXPORT_SYMBOL(tty_port_init); /** * tty_port_link_device - link tty and tty_port * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * * Provide the tty layer with a link from a tty (specified by @index) to a * tty_port (@port). Use this only if neither tty_port_register_device() nor * tty_port_install() is used in the driver. If used, this has to be called * before tty_register_driver(). */ void tty_port_link_device(struct tty_port *port, struct tty_driver *driver, unsigned index) { if (WARN_ON(index >= driver->num)) return; driver->ports[index] = port; } EXPORT_SYMBOL_GPL(tty_port_link_device); /** * tty_port_register_device - register tty device * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * @device: parent if exists, otherwise NULL * * It is the same as tty_register_device() except the provided @port is linked * to a concrete tty specified by @index. Use this or tty_port_install() (or * both). Call tty_port_link_device() as a last resort. */ struct device *tty_port_register_device(struct tty_port *port, struct tty_driver *driver, unsigned index, struct device *device) { return tty_port_register_device_attr(port, driver, index, device, NULL, NULL); } EXPORT_SYMBOL_GPL(tty_port_register_device); /** * tty_port_register_device_attr - register tty device * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * @device: parent if exists, otherwise NULL * @drvdata: Driver data to be set to device. * @attr_grp: Attribute group to be set on device. * * It is the same as tty_register_device_attr() except the provided @port is * linked to a concrete tty specified by @index. Use this or tty_port_install() * (or both). Call tty_port_link_device() as a last resort. */ struct device *tty_port_register_device_attr(struct tty_port *port, struct tty_driver *driver, unsigned index, struct device *device, void *drvdata, const struct attribute_group **attr_grp) { tty_port_link_device(port, driver, index); return tty_register_device_attr(driver, index, device, drvdata, attr_grp); } EXPORT_SYMBOL_GPL(tty_port_register_device_attr); /** * tty_port_register_device_attr_serdev - register tty or serdev device * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * @device: parent if exists, otherwise NULL * @drvdata: driver data for the device * @attr_grp: attribute group for the device * * Register a serdev or tty device depending on if the parent device has any * defined serdev clients or not. */ struct device *tty_port_register_device_attr_serdev(struct tty_port *port, struct tty_driver *driver, unsigned index, struct device *device, void *drvdata, const struct attribute_group **attr_grp) { struct device *dev; tty_port_link_device(port, driver, index); dev = serdev_tty_port_register(port, device, driver, index); if (PTR_ERR(dev) != -ENODEV) { /* Skip creating cdev if we registered a serdev device */ return dev; } return tty_register_device_attr(driver, index, device, drvdata, attr_grp); } EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev); /** * tty_port_register_device_serdev - register tty or serdev device * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * @device: parent if exists, otherwise NULL * * Register a serdev or tty device depending on if the parent device has any * defined serdev clients or not. */ struct device *tty_port_register_device_serdev(struct tty_port *port, struct tty_driver *driver, unsigned index, struct device *device) { return tty_port_register_device_attr_serdev(port, driver, index, device, NULL, NULL); } EXPORT_SYMBOL_GPL(tty_port_register_device_serdev); /** * tty_port_unregister_device - deregister a tty or serdev device * @port: tty_port of the device * @driver: tty_driver for this device * @index: index of the tty * * If a tty or serdev device is registered with a call to * tty_port_register_device_serdev() then this function must be called when * the device is gone. */ void tty_port_unregister_device(struct tty_port *port, struct tty_driver *driver, unsigned index) { int ret; ret = serdev_tty_port_unregister(port); if (ret == 0) return; tty_unregister_device(driver, index); } EXPORT_SYMBOL_GPL(tty_port_unregister_device); 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) { 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; return 0; } EXPORT_SYMBOL(tty_port_alloc_xmit_buf); void tty_port_free_xmit_buf(struct tty_port *port) { mutex_lock(&port->buf_mutex); free_page((unsigned long)port->xmit_buf); port->xmit_buf = NULL; INIT_KFIFO(port->xmit_fifo); mutex_unlock(&port->buf_mutex); } EXPORT_SYMBOL(tty_port_free_xmit_buf); /** * tty_port_destroy -- destroy inited port * @port: tty port to be destroyed * * When a port was initialized using tty_port_init(), one has to destroy the * port by this function. Either indirectly by using &tty_port refcounting * (tty_port_put()) or directly if refcounting is not used. */ void tty_port_destroy(struct tty_port *port) { tty_buffer_cancel_work(port); tty_buffer_free_all(port); } EXPORT_SYMBOL(tty_port_destroy); static void tty_port_destructor(struct kref *kref) { struct tty_port *port = container_of(kref, struct tty_port, kref); /* check if last port ref was dropped before tty release */ if (WARN_ON(port->itty)) return; free_page((unsigned long)port->xmit_buf); tty_port_destroy(port); if (port->ops && port->ops->destruct) port->ops->destruct(port); else kfree(port); } /** * tty_port_put -- drop a reference to tty_port * @port: port to drop a reference of (can be NULL) * * The final put will destroy and free up the @port using * @port->ops->destruct() hook, or using kfree() if not provided. */ void tty_port_put(struct tty_port *port) { if (port) kref_put(&port->kref, tty_port_destructor); } EXPORT_SYMBOL(tty_port_put); /** * tty_port_tty_get - get a tty reference * @port: tty port * * Return a refcount protected tty instance or %NULL if the port is not * associated with a tty (eg due to close or hangup). */ struct tty_struct *tty_port_tty_get(struct tty_port *port) { unsigned long flags; struct tty_struct *tty; spin_lock_irqsave(&port->lock, flags); tty = tty_kref_get(port->tty); spin_unlock_irqrestore(&port->lock, flags); return tty; } EXPORT_SYMBOL(tty_port_tty_get); /** * tty_port_tty_set - set the tty of a port * @port: tty port * @tty: the tty * * Associate the port and tty pair. Manages any internal refcounts. Pass %NULL * to deassociate a port. */ void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty) { unsigned long flags; spin_lock_irqsave(&port->lock, flags); tty_kref_put(port->tty); port->tty = tty_kref_get(tty); spin_unlock_irqrestore(&port->lock, flags); } EXPORT_SYMBOL(tty_port_tty_set); /** * tty_port_shutdown - internal helper to shutdown the device * @port: tty port to be shut down * @tty: the associated tty * * It is used by tty_port_hangup() and tty_port_close(). Its task is to * shutdown the device if it was initialized (note consoles remain * functioning). It lowers DTR/RTS (if @tty has HUPCL set) and invokes * @port->ops->shutdown(). */ static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty) { mutex_lock(&port->mutex); if (port->console) goto out; if (tty_port_initialized(port)) { tty_port_set_initialized(port, false); /* * Drop DTR/RTS if HUPCL is set. This causes any attached * modem to hang up the line. */ if (tty && C_HUPCL(tty)) tty_port_lower_dtr_rts(port); if (port->ops->shutdown) port->ops->shutdown(port); } out: mutex_unlock(&port->mutex); } /** * tty_port_hangup - hangup helper * @port: tty port * * Perform port level tty hangup flag and count changes. Drop the tty * reference. * * Caller holds tty lock. */ void tty_port_hangup(struct tty_port *port) { struct tty_struct *tty; unsigned long flags; spin_lock_irqsave(&port->lock, flags); port->count = 0; tty = port->tty; if (tty) set_bit(TTY_IO_ERROR, &tty->flags); port->tty = NULL; spin_unlock_irqrestore(&port->lock, flags); tty_port_set_active(port, false); tty_port_shutdown(port, tty); tty_kref_put(tty); wake_up_interruptible(&port->open_wait); wake_up_interruptible(&port->delta_msr_wait); } EXPORT_SYMBOL(tty_port_hangup); /** * tty_port_tty_hangup - helper to hang up a tty * @port: tty port * @check_clocal: hang only ttys with %CLOCAL unset? */ void tty_port_tty_hangup(struct tty_port *port, bool check_clocal) { struct tty_struct *tty = tty_port_tty_get(port); if (tty && (!check_clocal || !C_CLOCAL(tty))) tty_hangup(tty); tty_kref_put(tty); } EXPORT_SYMBOL_GPL(tty_port_tty_hangup); /** * tty_port_tty_wakeup - helper to wake up a tty * @port: tty port */ void tty_port_tty_wakeup(struct tty_port *port) { port->client_ops->write_wakeup(port); } EXPORT_SYMBOL_GPL(tty_port_tty_wakeup); /** * tty_port_carrier_raised - carrier raised check * @port: tty port * * Wrapper for the carrier detect logic. For the moment this is used * to hide some internal details. This will eventually become entirely * internal to the tty port. */ bool tty_port_carrier_raised(struct tty_port *port) { if (port->ops->carrier_raised == NULL) return true; return port->ops->carrier_raised(port); } EXPORT_SYMBOL(tty_port_carrier_raised); /** * tty_port_raise_dtr_rts - Raise DTR/RTS * @port: tty port * * Wrapper for the DTR/RTS raise logic. For the moment this is used to hide * some internal details. This will eventually become entirely internal to the * tty port. */ void tty_port_raise_dtr_rts(struct tty_port *port) { if (port->ops->dtr_rts) port->ops->dtr_rts(port, true); } EXPORT_SYMBOL(tty_port_raise_dtr_rts); /** * tty_port_lower_dtr_rts - Lower DTR/RTS * @port: tty port * * Wrapper for the DTR/RTS raise logic. For the moment this is used to hide * some internal details. This will eventually become entirely internal to the * tty port. */ void tty_port_lower_dtr_rts(struct tty_port *port) { if (port->ops->dtr_rts) port->ops->dtr_rts(port, false); } EXPORT_SYMBOL(tty_port_lower_dtr_rts); /** * tty_port_block_til_ready - Waiting logic for tty open * @port: the tty port being opened * @tty: the tty device being bound * @filp: the file pointer of the opener or %NULL * * Implement the core POSIX/SuS tty behaviour when opening a tty device. * Handles: * * - hangup (both before and during) * - non blocking open * - rts/dtr/dcd * - signals * - port flags and counts * * The passed @port must implement the @port->ops->carrier_raised method if it * can do carrier detect and the @port->ops->dtr_rts method if it supports * software management of these lines. Note that the dtr/rts raise is done each * iteration as a hangup may have previously dropped them while we wait. * * Caller holds tty lock. * * Note: May drop and reacquire tty lock when blocking, so @tty and @port may * have changed state (eg., may have been hung up). */ int tty_port_block_til_ready(struct tty_port *port, struct tty_struct *tty, struct file *filp) { int do_clocal = 0, retval; unsigned long flags; DEFINE_WAIT(wait); /* if non-blocking mode is set we can pass directly to open unless * the port has just hung up or is in another error state. */ if (tty_io_error(tty)) { tty_port_set_active(port, true); return 0; } if (filp == NULL || (filp->f_flags & O_NONBLOCK)) { /* Indicate we are open */ if (C_BAUD(tty)) tty_port_raise_dtr_rts(port); tty_port_set_active(port, true); return 0; } if (C_CLOCAL(tty)) do_clocal = 1; /* Block waiting until we can proceed. We may need to wait for the * carrier, but we must also wait for any close that is in progress * before the next open may complete. */ retval = 0; /* The port lock protects the port counts */ spin_lock_irqsave(&port->lock, flags); port->count--; port->blocked_open++; spin_unlock_irqrestore(&port->lock, flags); while (1) { /* Indicate we are open */ if (C_BAUD(tty) && tty_port_initialized(port)) tty_port_raise_dtr_rts(port); prepare_to_wait(&port->open_wait, &wait, TASK_INTERRUPTIBLE); /* Check for a hangup or uninitialised port. * Return accordingly. */ if (tty_hung_up_p(filp) || !tty_port_initialized(port)) { if (port->flags & ASYNC_HUP_NOTIFY) retval = -EAGAIN; else retval = -ERESTARTSYS; break; } /* * Probe the carrier. For devices with no carrier detect * tty_port_carrier_raised will always return true. * Never ask drivers if CLOCAL is set, this causes troubles * on some hardware. */ if (do_clocal || tty_port_carrier_raised(port)) break; if (signal_pending(current)) { retval = -ERESTARTSYS; break; } tty_unlock(tty); schedule(); tty_lock(tty); } finish_wait(&port->open_wait, &wait); /* Update counts. A parallel hangup will have set count to zero and * we must not mess that up further. */ spin_lock_irqsave(&port->lock, flags); if (!tty_hung_up_p(filp)) port->count++; port->blocked_open--; spin_unlock_irqrestore(&port->lock, flags); if (retval == 0) tty_port_set_active(port, true); return retval; } EXPORT_SYMBOL(tty_port_block_til_ready); static void tty_port_drain_delay(struct tty_port *port, struct tty_struct *tty) { unsigned int bps = tty_get_baud_rate(tty); long timeout; if (bps > 1200) { timeout = (HZ * 10 * port->drain_delay) / bps; timeout = max_t(long, timeout, HZ / 10); } else { timeout = 2 * HZ; } schedule_timeout_interruptible(timeout); } /** * tty_port_close_start - helper for tty->ops->close, part 1/2 * @port: tty_port of the device * @tty: tty being closed * @filp: passed file pointer * * Decrements and checks open count. Flushes the port if this is the last * close. That means, dropping the data from the outpu buffer on the device and * waiting for sending logic to finish. The rest of close handling is performed * in tty_port_close_end(). * * Locking: Caller holds tty lock. * * Return: 1 if this is the last close, otherwise 0 */ int tty_port_close_start(struct tty_port *port, struct tty_struct *tty, struct file *filp) { unsigned long flags; if (tty_hung_up_p(filp)) return 0; spin_lock_irqsave(&port->lock, flags); if (tty->count == 1 && port->count != 1) { tty_warn(tty, "%s: tty->count = 1 port count = %d\n", __func__, port->count); port->count = 1; } if (--port->count < 0) { tty_warn(tty, "%s: bad port count (%d)\n", __func__, port->count); port->count = 0; } if (port->count) { spin_unlock_irqrestore(&port->lock, flags); return 0; } spin_unlock_irqrestore(&port->lock, flags); tty->closing = 1; if (tty_port_initialized(port)) { /* Don't block on a stalled port, just pull the chain */ if (tty->flow.tco_stopped) tty_driver_flush_buffer(tty); if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE) tty_wait_until_sent(tty, port->closing_wait); if (port->drain_delay) tty_port_drain_delay(port, tty); } /* Flush the ldisc buffering */ tty_ldisc_flush(tty); /* Report to caller this is the last port reference */ return 1; } EXPORT_SYMBOL(tty_port_close_start); /** * tty_port_close_end - helper for tty->ops->close, part 2/2 * @port: tty_port of the device * @tty: tty being closed * * This is a continuation of the first part: tty_port_close_start(). This * should be called after turning off the device. It flushes the data from the * line discipline and delays the close by @port->close_delay. * * Locking: Caller holds tty lock. */ void tty_port_close_end(struct tty_port *port, struct tty_struct *tty) { unsigned long flags; tty_ldisc_flush(tty); tty->closing = 0; spin_lock_irqsave(&port->lock, flags); if (port->blocked_open) { spin_unlock_irqrestore(&port->lock, flags); if (port->close_delay) msleep_interruptible(jiffies_to_msecs(port->close_delay)); spin_lock_irqsave(&port->lock, flags); wake_up_interruptible(&port->open_wait); } spin_unlock_irqrestore(&port->lock, flags); tty_port_set_active(port, false); } EXPORT_SYMBOL(tty_port_close_end); /** * tty_port_close - generic tty->ops->close handler * @port: tty_port of the device * @tty: tty being closed * @filp: passed file pointer * * It is a generic helper to be used in driver's @tty->ops->close. It wraps a * sequence of tty_port_close_start(), tty_port_shutdown(), and * tty_port_close_end(). The latter two are called only if this is the last * close. See the respective functions for the details. * * Locking: Caller holds tty lock */ void tty_port_close(struct tty_port *port, struct tty_struct *tty, struct file *filp) { if (tty_port_close_start(port, tty, filp) == 0) return; tty_port_shutdown(port, tty); if (!port->console) set_bit(TTY_IO_ERROR, &tty->flags); tty_port_close_end(port, tty); tty_port_tty_set(port, NULL); } EXPORT_SYMBOL(tty_port_close); /** * tty_port_install - generic tty->ops->install handler * @port: tty_port of the device * @driver: tty_driver for this device * @tty: tty to be installed * * It is the same as tty_standard_install() except the provided @port is linked * to a concrete tty specified by @tty. Use this or tty_port_register_device() * (or both). Call tty_port_link_device() as a last resort. */ int tty_port_install(struct tty_port *port, struct tty_driver *driver, struct tty_struct *tty) { tty->port = port; return tty_standard_install(driver, tty); } EXPORT_SYMBOL_GPL(tty_port_install); /** * tty_port_open - generic tty->ops->open handler * @port: tty_port of the device * @tty: tty to be opened * @filp: passed file pointer * * It is a generic helper to be used in driver's @tty->ops->open. It activates * the devices using @port->ops->activate if not active already. And waits for * the device to be ready using tty_port_block_til_ready() (e.g. raises * DTR/CTS and waits for carrier). * * Note that @port->ops->shutdown is not called when @port->ops->activate * returns an error (on the contrary, @tty->ops->close is). * * Locking: Caller holds tty lock. * * Note: may drop and reacquire tty lock (in tty_port_block_til_ready()) so * @tty and @port may have changed state (eg., may be hung up now). */ int tty_port_open(struct tty_port *port, struct tty_struct *tty, struct file *filp) { spin_lock_irq(&port->lock); ++port->count; spin_unlock_irq(&port->lock); tty_port_tty_set(port, tty); /* * Do the device-specific open only if the hardware isn't * already initialized. Serialize open and shutdown using the * port mutex. */ mutex_lock(&port->mutex); if (!tty_port_initialized(port)) { clear_bit(TTY_IO_ERROR, &tty->flags); if (port->ops->activate) { int retval = port->ops->activate(port, tty); if (retval) { mutex_unlock(&port->mutex); return retval; } } tty_port_set_initialized(port, true); } mutex_unlock(&port->mutex); return tty_port_block_til_ready(port, tty, filp); } EXPORT_SYMBOL(tty_port_open);