diff options
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/drivers.rst | 654 |
1 files changed, 654 insertions, 0 deletions
diff --git a/Documentation/driver-api/drivers.rst b/Documentation/driver-api/drivers.rst new file mode 100644 index 000000000000..17f99d441b52 --- /dev/null +++ b/Documentation/driver-api/drivers.rst @@ -0,0 +1,654 @@ +==================== +Linux Device Drivers +==================== + +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: + +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: + +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: + +Message-based devices +===================== + +Fusion message devices +---------------------- + +.. kernel-doc:: drivers/message/fusion/mptbase.c + :export: + +.. kernel-doc:: drivers/message/fusion/mptbase.c + :internal: + +.. kernel-doc:: drivers/message/fusion/mptscsih.c + :export: + +.. kernel-doc:: drivers/message/fusion/mptscsih.c + :internal: + +.. kernel-doc:: drivers/message/fusion/mptctl.c + :internal: + +.. kernel-doc:: drivers/message/fusion/mptspi.c + :internal: + +.. kernel-doc:: drivers/message/fusion/mptfc.c + :internal: + +.. kernel-doc:: drivers/message/fusion/mptlan.c + :internal: + +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: + +16x50 UART Driver +================= + +.. kernel-doc:: drivers/tty/serial/serial_core.c + :export: + +.. kernel-doc:: drivers/tty/serial/8250/8250_core.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. + +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: + +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: + +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: + +High Speed Synchronous Serial Interface (HSI) +============================================= + +High Speed Synchronous Serial Interface (HSI) is a serial interface +mainly used for connecting application engines (APE) with cellular modem +engines (CMT) in cellular handsets. HSI provides multiplexing for up to +16 logical channels, low-latency and full duplex communication. + +.. kernel-doc:: include/linux/hsi/hsi.h + :internal: + +.. kernel-doc:: drivers/hsi/hsi_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: |