diff options
Diffstat (limited to 'Documentation/serial/driver')
| -rw-r--r-- | Documentation/serial/driver | 54 |
1 files changed, 36 insertions, 18 deletions
diff --git a/Documentation/serial/driver b/Documentation/serial/driver index 379468e12680..da193e092fc3 100644 --- a/Documentation/serial/driver +++ b/Documentation/serial/driver @@ -28,7 +28,7 @@ The serial core provides a few helper functions. This includes identifing the correct port structure (via uart_get_console) and decoding command line arguments (uart_parse_options). -There is also a helper function (uart_write_console) which performs a +There is also a helper function (uart_console_write) which performs a character by character write, translating newlines to CRLF sequences. Driver writers are recommended to use this function rather than implementing their own version. @@ -41,27 +41,23 @@ It is the responsibility of the low level hardware driver to perform the necessary locking using port->lock. There are some exceptions (which are described in the uart_ops listing below.) -There are three locks. A per-port spinlock, a per-port tmpbuf semaphore, -and an overall semaphore. +There are two locks. A per-port spinlock, and an overall semaphore. From the core driver perspective, the port->lock locks the following data: port->mctrl port->icount - info->xmit.head (circ->head) - info->xmit.tail (circ->tail) + port->state->xmit.head (circ_buf->head) + port->state->xmit.tail (circ_buf->tail) The low level driver is free to use this lock to provide any additional locking. -The core driver uses the info->tmpbuf_sem lock to prevent multi-threaded -access to the info->tmpbuf bouncebuffer used for port writes. - The port_sem semaphore is used to protect against ports being added/ removed or reconfigured at inappropriate times. Since v2.6.27, this semaphore has been the 'mutex' member of the tty_port struct, and -commonly referred to as the port mutex (or port->mutex). +commonly referred to as the port mutex. uart_ops @@ -135,6 +131,24 @@ hardware. Interrupts: locally disabled. This call must not sleep + throttle(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(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(port,ch) Transmit a high priority character, even if the port is stopped. This is used to implement XON/XOFF flow control and tcflow(). If @@ -172,9 +186,7 @@ hardware. should be terminated when another call is made with a zero ctl. - Locking: none. - Interrupts: caller dependent. - This call must not sleep + Locking: caller holds tty_port->mutex startup(port) Grab any interrupt resources and initialise any low level driver @@ -192,7 +204,7 @@ hardware. RTS nor DTR; this will have already been done via a separate call to set_mctrl. - Drivers must not access port->info once this call has completed. + 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. @@ -204,7 +216,7 @@ hardware. Flush any write buffers, reset any DMA state and stop any ongoing DMA transfers. - This will be called whenever the port->info->xmit circular + This will be called whenever the port->state->xmit circular buffer is cleared. Locking: port->lock taken. @@ -250,10 +262,15 @@ hardware. Other flags may be used (eg, xon/xoff characters) if your hardware supports hardware "soft" flow control. - Locking: caller holds port->mutex + Locking: caller holds tty_port->mutex Interrupts: caller dependent. This call must not sleep + set_ldisc(port,termios) + Notifier for discipline change. See Documentation/serial/tty.txt. + + Locking: caller holds tty_port->mutex + pm(port,state,oldstate) Perform any power management related activities on the specified port. State indicates the new state (defined by @@ -371,7 +388,7 @@ uart_get_baud_rate(port,termios,old,min,max) Interrupts: n/a uart_get_divisor(port,baud) - Return the divsor (baud_base / baud) for the specified baud + Return the divisor (baud_base / baud) for the specified baud rate, appropriately rounded. If 38400 baud and custom divisor is selected, return the @@ -449,11 +466,12 @@ mctrl_gpio_init(port, idx): mctrl_gpio_free(dev, gpios): This will free the requested gpios in mctrl_gpio_init(). - As devm_* function are used, there's generally no need to call + As devm_* functions are used, there's generally no need to call this function. mctrl_gpio_to_gpiod(gpios, gidx) - This returns the gpio structure associated to the modem line index. + This returns the gpio_desc structure associated to the modem line + index. mctrl_gpio_set(gpios, mctrl): This will sets the gpios according to the mctrl state. |