From f4cdf7ca9a1fdcca413157df19753f388a5a224e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Aug 2026 10:09:22 -0700 Subject: Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ... --- Documentation/driver-api/tty/index.rst | 75 ++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 Documentation/driver-api/tty/index.rst (limited to 'Documentation/driver-api/tty/index.rst') diff --git a/Documentation/driver-api/tty/index.rst b/Documentation/driver-api/tty/index.rst new file mode 100644 index 000000000..c1ffe3d1e --- /dev/null +++ b/Documentation/driver-api/tty/index.rst @@ -0,0 +1,75 @@ +.. 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 + tty_ioctl + tty_internals + console + +Writing TTY Driver +================== + +Before one starts writing a TTY driver, they must consider +:doc:`Serial <../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`. + +Other Documentation +=================== + +Miscellaneous documentation can be further found in these documents: + +.. toctree:: + :maxdepth: 2 + + moxa-smartio + n_gsm + n_tty -- cgit v1.3.1