diff options
Diffstat (limited to 'drivers/tty/tty_port.c')
| -rw-r--r-- | drivers/tty/tty_port.c | 796 |
1 files changed, 796 insertions, 0 deletions
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c new file mode 100644 index 000000000..dce08a6d7 --- /dev/null +++ b/drivers/tty/tty_port.c @@ -0,0 +1,796 @@ +// 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 int tty_port_default_receive_buf(struct tty_port *port, + const unsigned char *p, + const unsigned char *f, size_t count) +{ + int ret; + struct tty_struct *tty; + struct tty_ldisc *disc; + + tty = READ_ONCE(port->itty); + if (!tty) + return 0; + + disc = tty_ldisc_ref(tty); + if (!disc) + return 0; + + ret = tty_ldisc_receive_buf(disc, p, (char *)f, count); + + tty_ldisc_deref(disc); + + return ret; +} + +static void tty_port_default_lookahead_buf(struct tty_port *port, const unsigned char *p, + const unsigned char *f, unsigned int count) +{ + struct tty_struct *tty; + struct tty_ldisc *disc; + + tty = READ_ONCE(port->itty); + if (!tty) + return; + + disc = tty_ldisc_ref(tty); + if (!disc) + return; + + if (disc->ops->lookahead_buf) + disc->ops->lookahead_buf(disc->tty, p, f, count); + + tty_ldisc_deref(disc); +} + +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, 0); + /* + * 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, 0); + 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. + */ +int tty_port_carrier_raised(struct tty_port *port) +{ + if (port->ops->carrier_raised == NULL) + return 1; + 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, 1); +} +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, 0); +} +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, 1); + 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, 1); + 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, 1); + 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, 0); +} +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, 1); + } + mutex_unlock(&port->mutex); + return tty_port_block_til_ready(port, tty, filp); +} +EXPORT_SYMBOL(tty_port_open); |