diff options
57 files changed, 2720 insertions, 2320 deletions
diff --git a/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml b/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml index a90c971b4f1f..e7ac63dd1469 100644 --- a/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml +++ b/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml @@ -22,7 +22,9 @@ properties: - fsl,imx7ulp-lpuart - fsl,imx8qm-lpuart - items: - - const: fsl,imx8qxp-lpuart + - enum: + - fsl,imx8qxp-lpuart + - fsl,imx8ulp-lpuart - const: fsl,imx7ulp-lpuart reg: diff --git a/Documentation/devicetree/bindings/serial/renesas,sci.yaml b/Documentation/devicetree/bindings/serial/renesas,sci.yaml index 22ed2f0b1dc3..f00b1d38e9a5 100644 --- a/Documentation/devicetree/bindings/serial/renesas,sci.yaml +++ b/Documentation/devicetree/bindings/serial/renesas,sci.yaml @@ -14,7 +14,14 @@ allOf: properties: compatible: - const: renesas,sci + oneOf: + - items: + - enum: + - renesas,r9a07g044-sci # RZ/G2{L,LC} + - const: renesas,sci # generic SCI compatible UART + + - items: + - const: renesas,sci # generic SCI compatible UART reg: maxItems: 1 @@ -54,18 +61,45 @@ required: - clocks - clock-names +if: + properties: + compatible: + contains: + enum: + - renesas,r9a07g044-sci +then: + properties: + resets: + maxItems: 1 + + power-domains: + maxItems: 1 + + required: + - resets + - power-domains + unevaluatedProperties: false examples: - | + #include <dt-bindings/clock/r9a07g044-cpg.h> + #include <dt-bindings/interrupt-controller/arm-gic.h> + aliases { serial0 = &sci0; }; - sci0: serial@ffff78 { - compatible = "renesas,sci"; - reg = <0xffff78 8>; - interrupts = <88 0>, <89 0>, <90 0>, <91 0>; - clocks = <&fclk>; + sci0: serial@1004d000 { + compatible = "renesas,r9a07g044-sci", "renesas,sci"; + reg = <0x1004d000 0x400>; + interrupts = <GIC_SPI 405 IRQ_TYPE_LEVEL_HIGH>, + <GIC_SPI 406 IRQ_TYPE_LEVEL_HIGH>, + <GIC_SPI 407 IRQ_TYPE_LEVEL_HIGH>, + <GIC_SPI 408 IRQ_TYPE_LEVEL_HIGH>; + interrupt-names = "eri", "rxi", "txi", "tei"; + clocks = <&cpg CPG_MOD R9A07G044_SCI0_CLKP>; clock-names = "fck"; + power-domains = <&cpg>; + resets = <&cpg R9A07G044_SCI0_RST>; }; diff --git a/Documentation/devicetree/bindings/serial/renesas,scif.yaml b/Documentation/devicetree/bindings/serial/renesas,scif.yaml index 6b8731f7f2fb..21fbfa880e29 100644 --- a/Documentation/devicetree/bindings/serial/renesas,scif.yaml +++ b/Documentation/devicetree/bindings/serial/renesas,scif.yaml @@ -153,6 +153,7 @@ if: enum: - renesas,rcar-gen2-scif - renesas,rcar-gen3-scif + - renesas,scif-r9a07g044 then: required: - resets diff --git a/Documentation/driver-api/serial/index.rst b/Documentation/driver-api/serial/index.rst index 8f7d7af3b90b..7eb21a695fc3 100644 --- a/Documentation/driver-api/serial/index.rst +++ b/Documentation/driver-api/serial/index.rst @@ -9,7 +9,6 @@ Support for Serial devices driver - tty Serial drivers ============== diff --git a/Documentation/driver-api/serial/tty.rst b/Documentation/driver-api/serial/tty.rst deleted file mode 100644 index 4b709f392713..000000000000 --- a/Documentation/driver-api/serial/tty.rst +++ /dev/null @@ -1,328 +0,0 @@ -================= -The Lockronomicon -================= - -Your guide to the ancient and twisted locking policies of the tty layer and -the warped logic behind them. Beware all ye who read on. - - -Line Discipline ---------------- - -Line disciplines are registered with tty_register_ldisc() passing the -discipline number and the ldisc structure. At the point of registration the -discipline must be ready to use and it is possible it will get used before -the call returns success. If the call returns an error then it won't get -called. Do not re-use ldisc numbers as they are part of the userspace ABI -and writing over an existing ldisc will cause demons to eat your computer. -After the return the ldisc data has been copied so you may free your own -copy of the structure. You must not re-register over the top of the line -discipline even with the same data or your computer again will be eaten by -demons. - -In order to remove a line discipline call tty_unregister_ldisc(). -In ancient times this always worked. In modern times the function will -return -EBUSY if the ldisc is currently in use. Since the ldisc referencing -code manages the module counts this should not usually be a concern. - -Heed this warning: the reference count field of the registered copies of the -tty_ldisc structure in the ldisc table counts the number of lines using this -discipline. The reference count of the tty_ldisc structure within a tty -counts the number of active users of the ldisc at this instant. In effect it -counts the number of threads of execution within an ldisc method (plus those -about to enter and exit although this detail matters not). - -Line Discipline Methods ------------------------ - -TTY side interfaces -^^^^^^^^^^^^^^^^^^^ - -======================= ======================================================= -open() Called when the line discipline is attached to - the terminal. No other call into the line - discipline for this tty will occur until it - completes successfully. Should initialize any - state needed by the ldisc, and set receive_room - in the tty_struct to the maximum amount of data - the line discipline is willing to accept from the - driver with a single call to receive_buf(). - Returning an error will prevent the ldisc from - being attached. Can sleep. - -close() This is called on a terminal when the line - discipline is being unplugged. At the point of - execution no further users will enter the - ldisc code for this tty. Can sleep. - -hangup() Called when the tty line is hung up. - The line discipline should cease I/O to the tty. - No further calls into the ldisc code will occur. - Can sleep. - -read() (optional) A process requests reading data from - the line. Multiple read calls may occur in parallel - and the ldisc must deal with serialization issues. - If not defined, the process will receive an EIO - error. May sleep. - -write() (optional) A process requests writing data to the - line. Multiple write calls are serialized by the - tty layer for the ldisc. If not defined, the - process will receive an EIO error. May sleep. - -flush_buffer() (optional) May be called at any point between - open and close, and instructs the line discipline - to empty its input buffer. - -set_termios() (optional) Called on termios structure changes. - The caller passes the old termios data and the - current data is in the tty. Called under the - termios semaphore so allowed to sleep. Serialized - against itself only. - -poll() (optional) Check the status for the poll/select - calls. Multiple poll calls may occur in parallel. - May sleep. - -ioctl() (optional) Called when an ioctl is handed to the - tty layer that might be for the ldisc. Multiple - ioctl calls may occur in parallel. May sleep. - -compat_ioctl() (optional) Called when a 32 bit ioctl is handed - to the tty layer that might be for the ldisc. - Multiple ioctl calls may occur in parallel. - May sleep. -======================= ======================================================= - -Driver Side Interfaces -^^^^^^^^^^^^^^^^^^^^^^ - -======================= ======================================================= -receive_buf() (optional) Called by the low-level driver to hand - a buffer of received bytes to the ldisc for - processing. The number of bytes is guaranteed not - to exceed the current value of tty->receive_room. - All bytes must be processed. - -receive_buf2() (optional) Called by the low-level driver to hand - a buffer of received bytes to the ldisc for - processing. Returns the number of bytes processed. - - If both receive_buf() and receive_buf2() are - defined, receive_buf2() should be preferred. - -write_wakeup() May be called at any point between open and close. - The TTY_DO_WRITE_WAKEUP flag indicates if a call - is needed but always races versus calls. Thus the - ldisc must be careful about setting order and to - handle unexpected calls. Must not sleep. - - The driver is forbidden from calling this directly - from the ->write call from the ldisc as the ldisc - is permitted to call the driver write method from - this function. In such a situation defer it. - -dcd_change() Report to the tty line the current DCD pin status - changes and the relative timestamp. The timestamp - cannot be NULL. -======================= ======================================================= - - -Driver Access -^^^^^^^^^^^^^ - -Line discipline methods can call the following methods of the underlying -hardware driver through the function pointers within the tty->driver -structure: - -======================= ======================================================= -write() Write a block of characters to the tty device. - Returns the number of characters accepted. The - character buffer passed to this method is already - in kernel space. - -put_char() Queues a character for writing to the tty device. - If there is no room in the queue, the character is - ignored. - -flush_chars() (Optional) If defined, must be called after - queueing characters with put_char() in order to - start transmission. - -write_room() Returns the numbers of characters the tty driver - will accept for queueing to be written. - -ioctl() Invoke device specific ioctl. - Expects data pointers to refer to userspace. - Returns ENOIOCTLCMD for unrecognized ioctl numbers. - -set_termios() Notify the tty driver that the device's termios - settings have changed. New settings are in - tty->termios. Previous settings should be passed in - the "old" argument. - - The API is defined such that the driver should return - the actual modes selected. This means that the - driver function is responsible for modifying any - bits in the request it cannot fulfill to indicate - the actual modes being used. A device with no - hardware capability for change (e.g. a USB dongle or - virtual port) can provide NULL for this method. - -throttle() Notify the tty 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 tty. - -unthrottle() Notify the tty driver that characters can now be - sent to the tty without fear of overrunning the - input buffers of the line disciplines. - -stop() Ask the tty driver to stop outputting characters - to the tty device. - -start() Ask the tty driver to resume sending characters - to the tty device. - -hangup() Ask the tty driver to hang up the tty device. - -break_ctl() (Optional) Ask the tty driver to turn on or off - BREAK status on the RS-232 port. If state is -1, - then the BREAK status should be turned on; if - state is 0, then BREAK should be turned off. - If this routine is not implemented, use ioctls - TIOCSBRK / TIOCCBRK instead. - -wait_until_sent() Waits until the device has written out all of the - characters in its transmitter FIFO. - -send_xchar() Send a high-priority XON/XOFF character to the device. -======================= ======================================================= - - -Flags -^^^^^ - -Line discipline methods have access to tty->flags field containing the -following interesting flags: - -======================= ======================================================= -TTY_THROTTLED Driver input is throttled. The ldisc should call - tty->driver->unthrottle() in order to resume - reception when it is ready to process more data. - -TTY_DO_WRITE_WAKEUP If set, causes the driver to call the ldisc's - write_wakeup() method in order to resume - transmission when it can accept more data - to transmit. - -TTY_IO_ERROR If set, causes all subsequent userspace read/write - calls on the tty to fail, returning -EIO. - -TTY_OTHER_CLOSED Device is a pty and the other side has closed. - -TTY_NO_WRITE_SPLIT Prevent driver from splitting up writes into - smaller chunks. -======================= ======================================================= - - -Locking -^^^^^^^ - -Callers to the line discipline functions from the tty layer are required to -take line discipline locks. The same is true of calls from the driver side -but not yet enforced. - -Three calls are now provided:: - - ldisc = tty_ldisc_ref(tty); - -takes a handle to the line discipline in the tty and returns it. If no ldisc -is currently attached or the ldisc is being closed and re-opened at this -point then NULL is returned. While this handle is held the ldisc will not -change or go away:: - - tty_ldisc_deref(ldisc) - -Returns the ldisc reference and allows the ldisc to be closed. Returning the -reference takes away your right to call the ldisc functions until you take -a new reference:: - - ldisc = tty_ldisc_ref_wait(tty); - -Performs the same function as tty_ldisc_ref except that it will wait for an -ldisc change to complete and then return a reference to the new ldisc. - -While these functions are slightly slower than the old code they should have -minimal impact as most receive logic uses the flip buffers and they only -need to take a reference when they push bits up through the driver. - -A caution: The ldisc->open(), ldisc->close() and driver->set_ldisc -functions are called with the ldisc unavailable. Thus tty_ldisc_ref will -fail in this situation if used within these functions. Ldisc and driver -code calling its own functions must be careful in this case. - - -Driver Interface ----------------- - -======================= ======================================================= -open() Called when a device is opened. May sleep - -close() Called when a device is closed. At the point of - return from this call the driver must make no - further ldisc calls of any kind. May sleep - -write() Called to write bytes to the device. May not - sleep. May occur in parallel in special cases. - Because this includes panic paths drivers generally - shouldn't try and do clever locking here. - -put_char() Stuff a single character onto the queue. The - driver is guaranteed following up calls to - flush_chars. - -flush_chars() Ask the kernel to write put_char queue - -write_room() Return the number of characters that can be stuffed - into the port buffers without overflow (or less). - The ldisc is responsible for being intelligent - about multi-threading of write_room/write calls - -ioctl() Called when an ioctl may be for the driver - -set_termios() Called on termios change, serialized against - itself by a semaphore. May sleep. - -set_ldisc() Notifier for discipline change. At the point this - is done the discipline is not yet usable. Can now - sleep (I think) - -throttle() Called by the ldisc to ask the driver to do flow - control. Serialization including with unthrottle - is the job of the ldisc layer. - -unthrottle() Called by the ldisc to ask the driver to stop flow - control. - -stop() Ldisc notifier to the driver to stop output. As with - throttle the serializations with start() are down - to the ldisc layer. - -start() Ldisc notifier to the driver to start output. - -hangup() Ask the tty driver to cause a hangup initiated - from the host side. [Can sleep ??] - -break_ctl() Send RS232 break. Can sleep. Can get called in - parallel, driver must serialize (for now), and - with write calls. - -wait_until_sent() Wait for characters to exit the hardware queue - of the driver. Can sleep - -send_xchar() Send XON/XOFF and if possible jump the queue with - it in order to get fast flow control responses. - Cannot sleep ?? -======================= ======================================================= diff --git a/Documentation/index.rst b/Documentation/index.rst index 54ce34fd6fbd..2b4de3926858 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -137,6 +137,7 @@ needed). misc-devices/index scheduler/index mhi/index + tty/index Architecture-agnostic documentation ----------------------------------- diff --git a/Documentation/tty/index.rst b/Documentation/tty/index.rst new file mode 100644 index 000000000000..21ea0cb21e55 --- /dev/null +++ b/Documentation/tty/index.rst @@ -0,0 +1,63 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=== +TTY +=== + +Teletypewriter (TTY) layer takes care of all those serial devices. Including +the virtual ones like pseudoterminal (PTY). + +TTY structures +============== + +There are several major TTY structures. Every TTY device in a system has a +corresponding struct tty_port. These devices are maintained by a TTY driver +which is struct tty_driver. This structure describes the driver but also +contains a reference to operations which could be performed on the TTYs. It is +struct tty_operations. Then, upon open, a struct tty_struct is allocated and +lives until the final close. During this time, several callbacks from struct +tty_operations are invoked by the TTY layer. + +Every character received by the kernel (both from devices and users) is passed +through a preselected :doc:`tty_ldisc` (in +short ldisc; in C, struct tty_ldisc_ops). Its task is to transform characters +as defined by a particular ldisc or by user too. The default one is n_tty, +implementing echoes, signal handling, jobs control, special characters +processing, and more. The transformed characters are passed further to +user/device, depending on the source. + +In-detail description of the named TTY structures is in separate documents: + +.. toctree:: + :maxdepth: 2 + + tty_driver + tty_port + tty_struct + tty_ldisc + tty_buffer + n_tty + tty_internals + +Writing TTY Driver +================== + +Before one starts writing a TTY driver, they must consider +:doc:`Serial <../driver-api/serial/driver>` and :doc:`USB Serial +<../usb/usb-serial>` layers +first. Drivers for serial devices can often use one of these specific layers to +implement a serial driver. Only special devices should be handled directly by +the TTY Layer. If you are about to write such a driver, read on. + +A *typical* sequence a TTY driver performs is as follows: + +#. Allocate and register a TTY driver (module init) +#. Create and register TTY devices as they are probed (probe function) +#. Handle TTY operations and events like interrupts (TTY core invokes the + former, the device the latter) +#. Remove devices as they are going away (remove function) +#. Unregister and free the TTY driver (module exit) + +Steps regarding driver, i.e. 1., 3., and 5. are described in detail in +:doc:`tty_driver`. For the other two (devices handling), look into +:doc:`tty_port`. diff --git a/Documentation/tty/n_tty.rst b/Documentation/tty/n_tty.rst new file mode 100644 index 000000000000..15b70faee72d --- /dev/null +++ b/Documentation/tty/n_tty.rst @@ -0,0 +1,22 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===== +N_TTY +===== + +.. contents:: :local: + +The default (and fallback) :doc:`TTY line discipline <tty_ldisc>`. It tries to +handle characters as per POSIX. + +External Functions +================== + +.. kernel-doc:: drivers/tty/n_tty.c + :export: + +Internal Functions +================== + +.. kernel-doc:: drivers/tty/n_tty.c + :internal: diff --git a/Documentation/tty/tty_buffer.rst b/Documentation/tty/tty_buffer.rst new file mode 100644 index 000000000000..a39d4781e0d2 - |