| ==================== |
| 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: |
