Commit fd5d2b83 authored by Jonathan Corbet's avatar Jonathan Corbet

Merge branch 'driver-api' into doc/4.9

This short series convers device-drivers.tmpl into the RST format, splits
it up, and sets up the result under Documentation/driver-api/.  For added
fun, I've taken one top-level file (hsi.txt) and folded it into the
document as a way of showing the direction I'm thinking I would like things
to go.  There is plenty more of this sort of work that could be done, to
say the least - this is just a beginning!

The formatted results can be seen at:

    http://static.lwn.net/kerneldoc/driver-api/index.html

As part of the long-term task to turn Documentation/ into less of a horror
movie, I'd like to collect documentation of the driver-specific API here.
Arguably gpu/ and the media API stuff should eventually move here, though
we can discuss the color of that particular shed some other day.
Meanwhile, I'd appreciate comments on the general idea.
parents 829f4c36 d36bbab6
...@@ -6,7 +6,7 @@ ...@@ -6,7 +6,7 @@
# To add a new book the only step required is to add the book to the # To add a new book the only step required is to add the book to the
# list of DOCBOOKS. # list of DOCBOOKS.
DOCBOOKS := z8530book.xml device-drivers.xml \ DOCBOOKS := z8530book.xml \
kernel-hacking.xml kernel-locking.xml deviceiobook.xml \ kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
writing_usb_driver.xml networking.xml \ writing_usb_driver.xml networking.xml \
kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \ kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \
......
This diff is collapsed.
Driver Basics
=============
Driver Entry and Exit points
----------------------------
.. kernel-doc:: include/linux/init.h
:internal:
Atomic and pointer manipulation
-------------------------------
.. kernel-doc:: arch/x86/include/asm/atomic.h
:internal:
Delaying, scheduling, and timer routines
----------------------------------------
.. kernel-doc:: include/linux/sched.h
:internal:
.. kernel-doc:: kernel/sched/core.c
:export:
.. kernel-doc:: kernel/sched/cpupri.c
:internal:
.. kernel-doc:: kernel/sched/fair.c
:internal:
.. kernel-doc:: include/linux/completion.h
:internal:
.. kernel-doc:: kernel/time/timer.c
:export:
Wait queues and Wake events
---------------------------
.. kernel-doc:: include/linux/wait.h
:internal:
.. kernel-doc:: kernel/sched/wait.c
:export:
High-resolution timers
----------------------
.. kernel-doc:: include/linux/ktime.h
:internal:
.. kernel-doc:: include/linux/hrtimer.h
:internal:
.. kernel-doc:: kernel/time/hrtimer.c
:export:
Workqueues and Kevents
----------------------
.. kernel-doc:: include/linux/workqueue.h
:internal:
.. kernel-doc:: kernel/workqueue.c
:export:
Internal Functions
------------------
.. kernel-doc:: kernel/exit.c
:internal:
.. kernel-doc:: kernel/signal.c
:internal:
.. kernel-doc:: include/linux/kthread.h
:internal:
.. kernel-doc:: kernel/kthread.c
:export:
Kernel objects manipulation
---------------------------
.. kernel-doc:: lib/kobject.c
:export:
Kernel utility functions
------------------------
.. kernel-doc:: include/linux/kernel.h
:internal:
.. kernel-doc:: kernel/printk/printk.c
:export:
.. kernel-doc:: kernel/panic.c
:export:
.. kernel-doc:: kernel/sys.c
:export:
.. kernel-doc:: kernel/rcu/srcu.c
:export:
.. kernel-doc:: kernel/rcu/tree.c
:export:
.. kernel-doc:: kernel/rcu/tree_plugin.h
:export:
.. kernel-doc:: kernel/rcu/update.c
:export:
Device Resource Management
--------------------------
.. kernel-doc:: drivers/base/devres.c
:export:
Frame Buffer Library
====================
The frame buffer drivers depend heavily on four data structures. These
structures are declared in include/linux/fb.h. They are fb_info,
fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs. The last
three can be made available to and from userland.
fb_info defines the current state of a particular video card. Inside
fb_info, there exists a fb_ops structure which is a collection of
needed functions to make fbdev and fbcon work. fb_info is only visible
to the kernel.
fb_var_screeninfo is used to describe the features of a video card
that are user defined. With fb_var_screeninfo, things such as depth
and the resolution may be defined.
The next structure is fb_fix_screeninfo. This defines the properties
of a card that are created when a mode is set and can't be changed
otherwise. A good example of this is the start of the frame buffer
memory. This "locks" the address of the frame buffer memory, so that it
cannot be changed or moved.
The last structure is fb_monospecs. In the old API, there was little
importance for fb_monospecs. This allowed for forbidden things such as
setting a mode of 800x600 on a fix frequency monitor. With the new API,
fb_monospecs prevents such things, and if used correctly, can prevent a
monitor from being cooked. fb_monospecs will not be useful until
kernels 2.5.x.
Frame Buffer Memory
-------------------
.. kernel-doc:: drivers/video/fbdev/core/fbmem.c
:export:
Frame Buffer Colormap
---------------------
.. kernel-doc:: drivers/video/fbdev/core/fbcmap.c
:export:
Frame Buffer Video Mode Database
--------------------------------
.. kernel-doc:: drivers/video/fbdev/core/modedb.c
:internal:
.. kernel-doc:: drivers/video/fbdev/core/modedb.c
:export:
Frame Buffer Macintosh Video Mode Database
------------------------------------------
.. kernel-doc:: drivers/video/fbdev/macmodes.c
:export:
Frame Buffer Fonts
------------------
Refer to the file lib/fonts/fonts.c for more information.
HSI - High-speed Synchronous Serial Interface High Speed Synchronous Serial Interface (HSI)
=============================================
1. Introduction Introduction
~~~~~~~~~~~~~~~ ---------------
High Speed Syncronous Interface (HSI) is a fullduplex, low latency protocol, High Speed Syncronous Interface (HSI) is a fullduplex, low latency protocol,
that is optimized for die-level interconnect between an Application Processor that is optimized for die-level interconnect between an Application Processor
...@@ -17,25 +18,27 @@ signal can be used to wakeup the chips from standby modes. The signals are ...@@ -17,25 +18,27 @@ signal can be used to wakeup the chips from standby modes. The signals are
commonly prefixed by AC for signals going from the application die to the commonly prefixed by AC for signals going from the application die to the
cellular die and CA for signals going the other way around. cellular die and CA for signals going the other way around.
+------------+ +---------------+ ::
| Cellular | | Application |
| Die | | Die | +------------+ +---------------+
| | - - - - - - CAWAKE - - - - - - >| | | Cellular | | Application |
| T|------------ CADATA ------------>|R | | Die | | Die |
| X|------------ CAFLAG ------------>|X | | | - - - - - - CAWAKE - - - - - - >| |
| |<----------- ACREADY ------------| | | T|------------ CADATA ------------>|R |
| | | | | X|------------ CAFLAG ------------>|X |
| | | | | |<----------- ACREADY ------------| |
| |< - - - - - ACWAKE - - - - - - -| | | | | |
| R|<----------- ACDATA -------------|T | | | | |
| X|<----------- ACFLAG -------------|X | | |< - - - - - ACWAKE - - - - - - -| |
| |------------ CAREADY ----------->| | | R|<----------- ACDATA -------------|T |
| | | | | X|<----------- ACFLAG -------------|X |
| | | | | |------------ CAREADY ----------->| |
+------------+ +---------------+ | | | |
| | | |
2. HSI Subsystem in Linux +------------+ +---------------+
~~~~~~~~~~~~~~~~~~~~~~~~~
HSI Subsystem in Linux
-------------------------
In the Linux kernel the hsi subsystem is supposed to be used for HSI devices. In the Linux kernel the hsi subsystem is supposed to be used for HSI devices.
The hsi subsystem contains drivers for hsi controllers including support for The hsi subsystem contains drivers for hsi controllers including support for
...@@ -45,31 +48,41 @@ It also contains HSI client drivers, which make use of the generic API to ...@@ -45,31 +48,41 @@ It also contains HSI client drivers, which make use of the generic API to
implement a protocol used on the HSI interface. These client drivers can implement a protocol used on the HSI interface. These client drivers can
use an arbitrary number of channels. use an arbitrary number of channels.
3. hsi-char Device hsi-char Device
~~~~~~~~~~~~~~~~~~ ------------------
Each port automatically registers a generic client driver called hsi_char, Each port automatically registers a generic client driver called hsi_char,
which provides a charecter device for userspace representing the HSI port. which provides a charecter device for userspace representing the HSI port.
It can be used to communicate via HSI from userspace. Userspace may It can be used to communicate via HSI from userspace. Userspace may
configure the hsi_char device using the following ioctl commands: configure the hsi_char device using the following ioctl commands:
* HSC_RESET: HSC_RESET
- flush the HSI port flush the HSI port
* HSC_SET_PM HSC_SET_PM
- enable or disable the client. enable or disable the client.
* HSC_SEND_BREAK HSC_SEND_BREAK
- send break send break
* HSC_SET_RX HSC_SET_RX
- set RX configuration set RX configuration
* HSC_GET_RX HSC_GET_RX
- get RX configuration get RX configuration
* HSC_SET_TX HSC_SET_TX
- set TX configuration set TX configuration
HSC_GET_TX
get TX configuration
The kernel HSI API
------------------
.. kernel-doc:: include/linux/hsi/hsi.h
:internal:
.. kernel-doc:: drivers/hsi/hsi_core.c
:export:
* HSC_GET_TX
- get TX configuration
I\ :sup:`2`\ C and SMBus Subsystem
==================================
I\ :sup:`2`\ C (or without fancy typography, "I2C") is an acronym for
the "Inter-IC" bus, a simple bus protocol which is widely used where low
data rate communications suffice. Since it's also a licensed trademark,
some vendors use another name (such as "Two-Wire Interface", TWI) for
the same bus. I2C only needs two signals (SCL for clock, SDA for data),
conserving board real estate and minimizing signal quality issues. Most
I2C devices use seven bit addresses, and bus speeds of up to 400 kHz;
there's a high speed extension (3.4 MHz) that's not yet found wide use.
I2C is a multi-master bus; open drain signaling is used to arbitrate
between masters, as well as to handshake and to synchronize clocks from
slower clients.
The Linux I2C programming interfaces support only the master side of bus
interactions, not the slave side. The programming interface is
structured around two kinds of driver, and two kinds of device. An I2C
"Adapter Driver" abstracts the controller hardware; it binds to a
physical device (perhaps a PCI device or platform_device) and exposes a
:c:type:`struct i2c_adapter <i2c_adapter>` representing each
I2C bus segment it manages. On each I2C bus segment will be I2C devices
represented by a :c:type:`struct i2c_client <i2c_client>`.
Those devices will be bound to a :c:type:`struct i2c_driver
<i2c_driver>`, which should follow the standard Linux driver
model. (At this writing, a legacy model is more widely used.) There are
functions to perform various I2C protocol operations; at this writing
all such functions are usable only from task context.
The System Management Bus (SMBus) is a sibling protocol. Most SMBus
systems are also I2C conformant. The electrical constraints are tighter
for SMBus, and it standardizes particular protocol messages and idioms.
Controllers that support I2C can also support most SMBus operations, but
SMBus controllers don't support all the protocol options that an I2C
controller will. There are functions to perform various SMBus protocol
operations, either using I2C primitives or by issuing SMBus commands to
i2c_adapter devices which don't support those I2C operations.
.. kernel-doc:: include/linux/i2c.h
:internal:
.. kernel-doc:: drivers/i2c/i2c-boardinfo.c
:functions: i2c_register_board_info
.. kernel-doc:: drivers/i2c/i2c-core.c
:export:
========================================
The Linux driver implementer's API guide
========================================
The kernel offers a wide variety of interfaces to support the development
of device drivers. This document is an only somewhat organized collection
of some of those interfaces — it will hopefully get better over time! The
available subsections can be seen below.
.. class:: toc-title
Table of contents
.. toctree::
:maxdepth: 2
basics
infrastructure
message-based
sound
frame-buffer
input
spi
i2c
hsi
miscellaneous
Device drivers infrastructure
=============================
The Basic Device Driver-Model Structures
----------------------------------------
.. kernel-doc:: include/linux/device.h
:internal:
Device Drivers Base
-------------------
.. kernel-doc:: drivers/base/init.c
:internal:
.. kernel-doc:: drivers/base/driver.c
:export:
.. kernel-doc:: drivers/base/core.c
:export:
.. kernel-doc:: drivers/base/syscore.c
:export:
.. kernel-doc:: drivers/base/class.c
:export:
.. kernel-doc:: drivers/base/node.c
:internal:
.. kernel-doc:: drivers/base/firmware_class.c
:export:
.. kernel-doc:: drivers/base/transport_class.c
:export:
.. kernel-doc:: drivers/base/dd.c
:export:
.. kernel-doc:: include/linux/platform_device.h
:internal:
.. kernel-doc:: drivers/base/platform.c
:export:
.. kernel-doc:: drivers/base/bus.c
:export:
Buffer Sharing and Synchronization
----------------------------------
The dma-buf subsystem provides the framework for sharing buffers for
hardware (DMA) access across multiple device drivers and subsystems, and
for synchronizing asynchronous hardware access.
This is used, for example, by drm "prime" multi-GPU support, but is of
course not limited to GPU use cases.
The three main components of this are: (1) dma-buf, representing a
sg_table and exposed to userspace as a file descriptor to allow passing
between devices, (2) fence, which provides a mechanism to signal when
one device as finished access, and (3) reservation, which manages the
shared or exclusive fence(s) associated with the buffer.
dma-buf
~~~~~~~
.. kernel-doc:: drivers/dma-buf/dma-buf.c
:export:
.. kernel-doc:: include/linux/dma-buf.h
:internal:
reservation
~~~~~~~~~~~
.. kernel-doc:: drivers/dma-buf/reservation.c
:doc: Reservation Object Overview
.. kernel-doc:: drivers/dma-buf/reservation.c
:export:
.. kernel-doc:: include/linux/reservation.h
:internal:
fence
~~~~~
.. kernel-doc:: drivers/dma-buf/fence.c
:export:
.. kernel-doc:: include/linux/fence.h
:internal:
.. kernel-doc:: drivers/dma-buf/seqno-fence.c
:export:
.. kernel-doc:: include/linux/seqno-fence.h
:internal:
.. kernel-doc:: drivers/dma-buf/fence-array.c
:export:
.. kernel-doc:: include/linux/fence-array.h
:internal:
.. kernel-doc:: drivers/dma-buf/reservation.c
:export:
.. kernel-doc:: include/linux/reservation.h
:internal:
.. kernel-doc:: drivers/dma-buf/sync_file.c
:export:
.. kernel-doc:: include/linux/sync_file.h
:internal:
Device Drivers DMA Management
-----------------------------
.. kernel-doc:: drivers/base/dma-coherent.c
:export:
.. kernel-doc:: drivers/base/dma-mapping.c
:export:
Device Drivers Power Management
-------------------------------
.. kernel-doc:: drivers/base/power/main.c
:export:
Device Drivers ACPI Support
---------------------------
.. kernel-doc:: drivers/acpi/scan.c
:export:
.. kernel-doc:: drivers/acpi/scan.c
:internal:
Device drivers PnP support
--------------------------
.. kernel-doc:: drivers/pnp/core.c
:internal:
.. kernel-doc:: drivers/pnp/card.c
:export:
.. kernel-doc:: drivers/pnp/driver.c
:internal:
.. kernel-doc:: drivers/pnp/manager.c
:export:
.. kernel-doc:: drivers/pnp/support.c
:export:
Userspace IO devices
--------------------
.. kernel-doc:: drivers/uio/uio.c
:export:
.. kernel-doc:: include/linux/uio_driver.h
:internal:
Input Subsystem
===============
Input core
----------
.. kernel-doc:: include/linux/input.h
:internal:
.. kernel-doc:: drivers/input/input.c
:export:
.. kernel-doc:: drivers/input/ff-core.c
:export:
.. kernel-doc:: drivers/input/ff-memless.c
:export:
Multitouch Library
------------------
.. kernel-doc:: include/linux/input/mt.h
:internal:
.. kernel-doc:: drivers/input/input-mt.c
:export:
Polled input devices
--------------------
.. kernel-doc:: include/linux/input-polldev.h
:internal:
.. kernel-doc:: drivers/input/input-polldev.c
:export:
Matrix keyboards/keypads
------------------------
.. kernel-doc:: include/linux/input/matrix_keypad.h
:internal:
Sparse keymap support
---------------------
.. kernel-doc:: include/linux/input/sparse-keymap.h
:internal:
.. kernel-doc:: drivers/input/sparse-keymap.c
:export:
Message-based devices
=====================
Fusion message devices
----------------------
.. kernel-doc:: drivers/message/fusion/mptbase.c
:export:
.. kernel-doc:: drivers/message/fusion/mptscsih.c
:export:
Parallel Port Devices
=====================
.. kernel-doc:: include/linux/parport.h
:internal:
.. kernel-doc:: drivers/parport/ieee1284.c
:export:
.. kernel-doc:: drivers/parport/share.c
:export:
.. kernel-doc:: drivers/parport/daisy.c
:internal:
16x50 UART Driver
=================
.. kernel-doc:: drivers/tty/serial/serial_core.c
:export:
.. kernel-doc:: drivers/tty/serial/8250/8250_core.c
:export:
Pulse-Width Modulation (PWM)
============================
Pulse-width modulation is a modulation technique primarily used to
control power supplied to electrical devices.
The PWM framework provides an abstraction for providers and consumers of
PWM signals. A controller that provides one or more PWM signals is
registered as :c:type:`struct pwm_chip <pwm_chip>`. Providers
are expected to embed this structure in a driver-specific structure.
This structure contains fields that describe a particular chip.
A chip exposes one or more PWM signal sources, each of which exposed as
a :c:type:`struct pwm_device <pwm_device>`. Operations can be
performed on PWM devices to control the period, duty cycle, polarity and
active state of the signal.
Note that PWM devices are exclusive resources: they can always only be
used by one consumer at a time.
.. kernel-doc:: include/linux/pwm.h
:internal:
.. kernel-doc:: drivers/pwm/core.c
:export:
Sound Devices
=============
.. kernel-doc:: include/sound/core.h
:internal:
.. kernel-doc:: sound/sound_core.c
:export:
.. kernel-doc:: include/sound/pcm.h
:internal:
.. kernel-doc:: sound/core/pcm.c
:export:
.. kernel-doc:: sound/core/device.c
:export:
.. kernel-doc:: sound/core/info.c
:export:
.. kernel-doc:: sound/core/rawmidi.c
:export:
.. kernel-doc:: sound/core/sound.c
:export:
.. kernel-doc:: sound/core/memory.c
:export:
.. kernel-doc:: sound/core/pcm_memory.c
:export:
.. kernel-doc:: sound/core/init.c
:export:
.. kernel-doc:: sound/core/isadma.c
:export:
.. kernel-doc:: sound/core/control.c
:export:
.. kernel-doc:: sound/core/pcm_lib.c
:export:
.. kernel-doc:: sound/core/hwdep.c
:export:
.. kernel-doc:: sound/core/pcm_native.c
:export:
.. kernel-doc:: sound/core/memalloc.c
:export:
Serial Peripheral Interface (SPI)
=================================
SPI is the "Serial Peripheral Interface", widely used with embedded
systems because it is a simple and efficient interface: basically a
multiplexed shift register. Its three signal wires hold a clock (SCK,
often in the range of 1-20 MHz), a "Master Out, Slave In" (MOSI) data
line, and a "Master In, Slave Out" (MISO) data line. SPI is a full
duplex protocol; for each bit shifted out the MOSI line (one per clock)
another is shifted in on the MISO line. Those bits are assembled into
words of various sizes on the way to and from system memory. An
additional chipselect line is usually active-low (nCS); four signals are
normally used for each peripheral, plus sometimes an interrupt.
The SPI bus facilities listed here provide a generalized interface to
declare SPI busses and devices, manage them according to the standard
Linux driver model, and perform input/output operations. At this time,
only "master" side interfaces are supported, where Linux talks to SPI
peripherals and does not implement such a peripheral itself. (Interfaces
to support implementing SPI slaves would necessarily look different.)
The programming interface is structured around two kinds of driver, and
two kinds of device. A "Controller Driver" abstracts the controller
hardware, which may be as simple as a set of GPIO pins or as complex as
a pair of FIFOs connected to dual DMA engines on the other side of the
SPI shift register (maximizing throughput). Such drivers bridge between
whatever bus they sit on (often the platform bus) and SPI, and expose
the SPI side of their device as a :c:type:`struct spi_master
<spi_master>`. SPI devices are children of that master,
represented as a :c:type:`struct spi_device <spi_device>` and
manufactured from :c:type:`struct spi_board_info
<spi_board_info>` descriptors which are usually provided by
board-specific initialization code. A :c:type:`struct spi_driver
<spi_driver>` is called a "Protocol Driver", and is bound to a
spi_device using normal driver model calls.
The I/O model is a set of queued messages. Protocol drivers submit one
or more :c:type:`struct spi_message <spi_message>` objects,
which are processed and completed asynchronously. (There are synchronous
wrappers, however.) Messages are built from one or more
:c:type:`struct spi_transfer <spi_transfer>` objects, each of
which wraps a full duplex SPI transfer. A variety of protocol tweaking
options are needed, because different chips adopt very different
policies for how they use the bits transferred with SPI.
.. kernel-doc:: include/linux/spi/spi.h
:internal:
.. kernel-doc:: drivers/spi/spi.c
:functions: spi_register_board_info
.. kernel-doc:: drivers/spi/spi.c
:export:
...@@ -13,6 +13,7 @@ Contents: ...@@ -13,6 +13,7 @@ Contents:
kernel-documentation kernel-documentation
dev-tools/tools dev-tools/tools
driver-api/index
media/index media/index
gpu/index gpu/index
......
...@@ -5606,7 +5606,7 @@ M: Sebastian Reichel <sre@kernel.org> ...@@ -5606,7 +5606,7 @@ M: Sebastian Reichel <sre@kernel.org>
T: git git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-hsi.git T: git git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-hsi.git
S: Maintained S: Maintained
F: Documentation/ABI/testing/sysfs-bus-hsi F: Documentation/ABI/testing/sysfs-bus-hsi
F: Documentation/hsi.txt F: Documentation/device-drivers/serial-interfaces.rst
F: drivers/hsi/ F: drivers/hsi/
F: include/linux/hsi/ F: include/linux/hsi/
F: include/uapi/linux/hsi/ F: include/uapi/linux/hsi/
......
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