mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-19 10:44:14 +08:00
33e34dc6ee
Various documentation updates for the SPI infrastructure, to clarify things that may not have been clear, to cope with lack of editing, and fix omissions. Also, plug SPI into the kernel-api DocBook template, and fix all the resulting glitches in document generation. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: "Randy.Dunlap" <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
643 lines
18 KiB
XML
643 lines
18 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
|
|
|
|
<book id="LinuxKernelAPI">
|
|
<bookinfo>
|
|
<title>The Linux Kernel API</title>
|
|
|
|
<legalnotice>
|
|
<para>
|
|
This documentation is free software; you can redistribute
|
|
it and/or modify it under the terms of the GNU General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2 of the License, or (at your option) any later
|
|
version.
|
|
</para>
|
|
|
|
<para>
|
|
This program is distributed in the hope that it will be
|
|
useful, but WITHOUT ANY WARRANTY; without even the implied
|
|
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
|
|
See the GNU General Public License for more details.
|
|
</para>
|
|
|
|
<para>
|
|
You should have received a copy of the GNU General Public
|
|
License along with this program; if not, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
|
|
MA 02111-1307 USA
|
|
</para>
|
|
|
|
<para>
|
|
For more details see the file COPYING in the source
|
|
distribution of Linux.
|
|
</para>
|
|
</legalnotice>
|
|
</bookinfo>
|
|
|
|
<toc></toc>
|
|
|
|
<chapter id="Basics">
|
|
<title>Driver Basics</title>
|
|
<sect1><title>Driver Entry and Exit points</title>
|
|
!Iinclude/linux/init.h
|
|
</sect1>
|
|
|
|
<sect1><title>Atomic and pointer manipulation</title>
|
|
!Iinclude/asm-i386/atomic.h
|
|
!Iinclude/asm-i386/unaligned.h
|
|
</sect1>
|
|
|
|
<sect1><title>Delaying, scheduling, and timer routines</title>
|
|
!Iinclude/linux/sched.h
|
|
!Ekernel/sched.c
|
|
!Ekernel/timer.c
|
|
</sect1>
|
|
<sect1><title>High-resolution timers</title>
|
|
!Iinclude/linux/ktime.h
|
|
!Iinclude/linux/hrtimer.h
|
|
!Ekernel/hrtimer.c
|
|
</sect1>
|
|
<sect1><title>Workqueues and Kevents</title>
|
|
!Ekernel/workqueue.c
|
|
</sect1>
|
|
<sect1><title>Internal Functions</title>
|
|
!Ikernel/exit.c
|
|
!Ikernel/signal.c
|
|
!Iinclude/linux/kthread.h
|
|
!Ekernel/kthread.c
|
|
</sect1>
|
|
|
|
<sect1><title>Kernel objects manipulation</title>
|
|
<!--
|
|
X!Iinclude/linux/kobject.h
|
|
-->
|
|
!Elib/kobject.c
|
|
</sect1>
|
|
|
|
<sect1><title>Kernel utility functions</title>
|
|
!Iinclude/linux/kernel.h
|
|
!Ekernel/printk.c
|
|
!Ekernel/panic.c
|
|
!Ekernel/sys.c
|
|
!Ekernel/rcupdate.c
|
|
</sect1>
|
|
|
|
</chapter>
|
|
|
|
<chapter id="adt">
|
|
<title>Data Types</title>
|
|
<sect1><title>Doubly Linked Lists</title>
|
|
!Iinclude/linux/list.h
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="libc">
|
|
<title>Basic C Library Functions</title>
|
|
|
|
<para>
|
|
When writing drivers, you cannot in general use routines which are
|
|
from the C Library. Some of the functions have been found generally
|
|
useful and they are listed below. The behaviour of these functions
|
|
may vary slightly from those defined by ANSI, and these deviations
|
|
are noted in the text.
|
|
</para>
|
|
|
|
<sect1><title>String Conversions</title>
|
|
!Ilib/vsprintf.c
|
|
!Elib/vsprintf.c
|
|
</sect1>
|
|
<sect1><title>String Manipulation</title>
|
|
<!-- All functions are exported at now
|
|
X!Ilib/string.c
|
|
-->
|
|
!Elib/string.c
|
|
</sect1>
|
|
<sect1><title>Bit Operations</title>
|
|
!Iinclude/asm-i386/bitops.h
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="kernel-lib">
|
|
<title>Basic Kernel Library Functions</title>
|
|
|
|
<para>
|
|
The Linux kernel provides more basic utility functions.
|
|
</para>
|
|
|
|
<sect1><title>Bitmap Operations</title>
|
|
!Elib/bitmap.c
|
|
!Ilib/bitmap.c
|
|
</sect1>
|
|
|
|
<sect1><title>Command-line Parsing</title>
|
|
!Elib/cmdline.c
|
|
</sect1>
|
|
|
|
<sect1><title>CRC Functions</title>
|
|
!Elib/crc16.c
|
|
!Elib/crc32.c
|
|
!Elib/crc-ccitt.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="mm">
|
|
<title>Memory Management in Linux</title>
|
|
<sect1><title>The Slab Cache</title>
|
|
!Iinclude/linux/slab.h
|
|
!Emm/slab.c
|
|
</sect1>
|
|
<sect1><title>User Space Memory Access</title>
|
|
!Iinclude/asm-i386/uaccess.h
|
|
!Earch/i386/lib/usercopy.c
|
|
</sect1>
|
|
<sect1><title>More Memory Management Functions</title>
|
|
!Iinclude/linux/rmap.h
|
|
!Emm/readahead.c
|
|
!Emm/filemap.c
|
|
!Emm/memory.c
|
|
!Emm/vmalloc.c
|
|
!Imm/page_alloc.c
|
|
!Emm/mempool.c
|
|
!Emm/page-writeback.c
|
|
!Emm/truncate.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
|
|
<chapter id="ipc">
|
|
<title>Kernel IPC facilities</title>
|
|
|
|
<sect1><title>IPC utilities</title>
|
|
!Iipc/util.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="kfifo">
|
|
<title>FIFO Buffer</title>
|
|
<sect1><title>kfifo interface</title>
|
|
!Iinclude/linux/kfifo.h
|
|
!Ekernel/kfifo.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="relayfs">
|
|
<title>relay interface support</title>
|
|
|
|
<para>
|
|
Relay interface support
|
|
is designed to provide an efficient mechanism for tools and
|
|
facilities to relay large amounts of data from kernel space to
|
|
user space.
|
|
</para>
|
|
|
|
<sect1><title>relay interface</title>
|
|
!Ekernel/relay.c
|
|
!Ikernel/relay.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="netcore">
|
|
<title>Linux Networking</title>
|
|
<sect1><title>Networking Base Types</title>
|
|
!Iinclude/linux/net.h
|
|
</sect1>
|
|
<sect1><title>Socket Buffer Functions</title>
|
|
!Iinclude/linux/skbuff.h
|
|
!Iinclude/net/sock.h
|
|
!Enet/socket.c
|
|
!Enet/core/skbuff.c
|
|
!Enet/core/sock.c
|
|
!Enet/core/datagram.c
|
|
!Enet/core/stream.c
|
|
</sect1>
|
|
<sect1><title>Socket Filter</title>
|
|
!Enet/core/filter.c
|
|
</sect1>
|
|
<sect1><title>Generic Network Statistics</title>
|
|
!Iinclude/linux/gen_stats.h
|
|
!Enet/core/gen_stats.c
|
|
!Enet/core/gen_estimator.c
|
|
</sect1>
|
|
<sect1><title>SUN RPC subsystem</title>
|
|
<!-- The !D functionality is not perfect, garbage has to be protected by comments
|
|
!Dnet/sunrpc/sunrpc_syms.c
|
|
-->
|
|
!Enet/sunrpc/xdr.c
|
|
!Enet/sunrpc/svcsock.c
|
|
!Enet/sunrpc/sched.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="netdev">
|
|
<title>Network device support</title>
|
|
<sect1><title>Driver Support</title>
|
|
!Enet/core/dev.c
|
|
!Enet/ethernet/eth.c
|
|
!Iinclude/linux/etherdevice.h
|
|
!Edrivers/net/phy/phy.c
|
|
!Idrivers/net/phy/phy.c
|
|
!Edrivers/net/phy/phy_device.c
|
|
!Idrivers/net/phy/phy_device.c
|
|
!Edrivers/net/phy/mdio_bus.c
|
|
!Idrivers/net/phy/mdio_bus.c
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Enet/core/wireless.c
|
|
-->
|
|
</sect1>
|
|
<sect1><title>Synchronous PPP</title>
|
|
!Edrivers/net/wan/syncppp.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="modload">
|
|
<title>Module Support</title>
|
|
<sect1><title>Module Loading</title>
|
|
!Ekernel/kmod.c
|
|
</sect1>
|
|
<sect1><title>Inter Module support</title>
|
|
<para>
|
|
Refer to the file kernel/module.c for more information.
|
|
</para>
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Ekernel/module.c
|
|
-->
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="hardware">
|
|
<title>Hardware Interfaces</title>
|
|
<sect1><title>Interrupt Handling</title>
|
|
!Ekernel/irq/manage.c
|
|
</sect1>
|
|
|
|
<sect1><title>DMA Channels</title>
|
|
!Ekernel/dma.c
|
|
</sect1>
|
|
|
|
<sect1><title>Resources Management</title>
|
|
!Ikernel/resource.c
|
|
!Ekernel/resource.c
|
|
</sect1>
|
|
|
|
<sect1><title>MTRR Handling</title>
|
|
!Earch/i386/kernel/cpu/mtrr/main.c
|
|
</sect1>
|
|
|
|
<sect1><title>PCI Support Library</title>
|
|
!Edrivers/pci/pci.c
|
|
!Edrivers/pci/pci-driver.c
|
|
!Edrivers/pci/remove.c
|
|
!Edrivers/pci/pci-acpi.c
|
|
!Edrivers/pci/search.c
|
|
!Edrivers/pci/msi.c
|
|
!Edrivers/pci/bus.c
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Edrivers/pci/hotplug.c
|
|
-->
|
|
!Edrivers/pci/probe.c
|
|
!Edrivers/pci/rom.c
|
|
</sect1>
|
|
<sect1><title>PCI Hotplug Support Library</title>
|
|
!Edrivers/pci/hotplug/pci_hotplug_core.c
|
|
</sect1>
|
|
<sect1><title>MCA Architecture</title>
|
|
<sect2><title>MCA Device Functions</title>
|
|
<para>
|
|
Refer to the file arch/i386/kernel/mca.c for more information.
|
|
</para>
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Earch/i386/kernel/mca.c
|
|
-->
|
|
</sect2>
|
|
<sect2><title>MCA Bus DMA</title>
|
|
!Iinclude/asm-i386/mca_dma.h
|
|
</sect2>
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="firmware">
|
|
<title>Firmware Interfaces</title>
|
|
<sect1><title>DMI Interfaces</title>
|
|
!Edrivers/firmware/dmi_scan.c
|
|
</sect1>
|
|
<sect1><title>EDD Interfaces</title>
|
|
!Idrivers/firmware/edd.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="security">
|
|
<title>Security Framework</title>
|
|
!Esecurity/security.c
|
|
</chapter>
|
|
|
|
<chapter id="audit">
|
|
<title>Audit Interfaces</title>
|
|
!Ekernel/audit.c
|
|
!Ikernel/auditsc.c
|
|
!Ikernel/auditfilter.c
|
|
</chapter>
|
|
|
|
<chapter id="accounting">
|
|
<title>Accounting Framework</title>
|
|
!Ikernel/acct.c
|
|
</chapter>
|
|
|
|
<chapter id="pmfuncs">
|
|
<title>Power Management</title>
|
|
!Ekernel/power/pm.c
|
|
</chapter>
|
|
|
|
<chapter id="devdrivers">
|
|
<title>Device drivers infrastructure</title>
|
|
<sect1><title>Device Drivers Base</title>
|
|
<!--
|
|
X!Iinclude/linux/device.h
|
|
-->
|
|
!Edrivers/base/driver.c
|
|
!Edrivers/base/core.c
|
|
!Edrivers/base/class.c
|
|
!Edrivers/base/firmware_class.c
|
|
!Edrivers/base/transport_class.c
|
|
!Edrivers/base/dmapool.c
|
|
<!-- Cannot be included, because
|
|
attribute_container_add_class_device_adapter
|
|
and attribute_container_classdev_to_container
|
|
exceed allowed 44 characters maximum
|
|
X!Edrivers/base/attribute_container.c
|
|
-->
|
|
!Edrivers/base/sys.c
|
|
<!--
|
|
X!Edrivers/base/interface.c
|
|
-->
|
|
!Edrivers/base/platform.c
|
|
!Edrivers/base/bus.c
|
|
</sect1>
|
|
<sect1><title>Device Drivers Power Management</title>
|
|
!Edrivers/base/power/main.c
|
|
!Edrivers/base/power/resume.c
|
|
!Edrivers/base/power/suspend.c
|
|
</sect1>
|
|
<sect1><title>Device Drivers ACPI Support</title>
|
|
<!-- Internal functions only
|
|
X!Edrivers/acpi/sleep/main.c
|
|
X!Edrivers/acpi/sleep/wakeup.c
|
|
X!Edrivers/acpi/motherboard.c
|
|
X!Edrivers/acpi/bus.c
|
|
-->
|
|
!Edrivers/acpi/scan.c
|
|
!Idrivers/acpi/scan.c
|
|
<!-- No correct structured comments
|
|
X!Edrivers/acpi/pci_bind.c
|
|
-->
|
|
</sect1>
|
|
<sect1><title>Device drivers PnP support</title>
|
|
!Edrivers/pnp/core.c
|
|
<!-- No correct structured comments
|
|
X!Edrivers/pnp/system.c
|
|
-->
|
|
!Edrivers/pnp/card.c
|
|
!Edrivers/pnp/driver.c
|
|
!Edrivers/pnp/manager.c
|
|
!Edrivers/pnp/support.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="blkdev">
|
|
<title>Block Devices</title>
|
|
!Eblock/ll_rw_blk.c
|
|
</chapter>
|
|
|
|
<chapter id="chrdev">
|
|
<title>Char devices</title>
|
|
!Efs/char_dev.c
|
|
</chapter>
|
|
|
|
<chapter id="miscdev">
|
|
<title>Miscellaneous Devices</title>
|
|
!Edrivers/char/misc.c
|
|
</chapter>
|
|
|
|
<chapter id="parportdev">
|
|
<title>Parallel Port Devices</title>
|
|
!Iinclude/linux/parport.h
|
|
!Edrivers/parport/ieee1284.c
|
|
!Edrivers/parport/share.c
|
|
!Idrivers/parport/daisy.c
|
|
</chapter>
|
|
|
|
<chapter id="message_devices">
|
|
<title>Message-based devices</title>
|
|
<sect1><title>Fusion message devices</title>
|
|
!Edrivers/message/fusion/mptbase.c
|
|
!Idrivers/message/fusion/mptbase.c
|
|
!Edrivers/message/fusion/mptscsih.c
|
|
!Idrivers/message/fusion/mptscsih.c
|
|
!Idrivers/message/fusion/mptctl.c
|
|
!Idrivers/message/fusion/mptspi.c
|
|
!Idrivers/message/fusion/mptfc.c
|
|
!Idrivers/message/fusion/mptlan.c
|
|
</sect1>
|
|
<sect1><title>I2O message devices</title>
|
|
!Iinclude/linux/i2o.h
|
|
!Idrivers/message/i2o/core.h
|
|
!Edrivers/message/i2o/iop.c
|
|
!Idrivers/message/i2o/iop.c
|
|
!Idrivers/message/i2o/config-osm.c
|
|
!Edrivers/message/i2o/exec-osm.c
|
|
!Idrivers/message/i2o/exec-osm.c
|
|
!Idrivers/message/i2o/bus-osm.c
|
|
!Edrivers/message/i2o/device.c
|
|
!Idrivers/message/i2o/device.c
|
|
!Idrivers/message/i2o/driver.c
|
|
!Idrivers/message/i2o/pci.c
|
|
!Idrivers/message/i2o/i2o_block.c
|
|
!Idrivers/message/i2o/i2o_scsi.c
|
|
!Idrivers/message/i2o/i2o_proc.c
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="snddev">
|
|
<title>Sound Devices</title>
|
|
!Iinclude/sound/core.h
|
|
!Esound/sound_core.c
|
|
!Iinclude/sound/pcm.h
|
|
!Esound/core/pcm.c
|
|
!Esound/core/device.c
|
|
!Esound/core/info.c
|
|
!Esound/core/rawmidi.c
|
|
!Esound/core/sound.c
|
|
!Esound/core/memory.c
|
|
!Esound/core/pcm_memory.c
|
|
!Esound/core/init.c
|
|
!Esound/core/isadma.c
|
|
!Esound/core/control.c
|
|
!Esound/core/pcm_lib.c
|
|
!Esound/core/hwdep.c
|
|
!Esound/core/pcm_native.c
|
|
!Esound/core/memalloc.c
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Isound/sound_firmware.c
|
|
-->
|
|
</chapter>
|
|
|
|
<chapter id="uart16x50">
|
|
<title>16x50 UART Driver</title>
|
|
!Iinclude/linux/serial_core.h
|
|
!Edrivers/serial/serial_core.c
|
|
!Edrivers/serial/8250.c
|
|
</chapter>
|
|
|
|
<chapter id="z85230">
|
|
<title>Z85230 Support Library</title>
|
|
!Edrivers/net/wan/z85230.c
|
|
</chapter>
|
|
|
|
<chapter id="fbdev">
|
|
<title>Frame Buffer Library</title>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<para>
|
|
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.
|
|
</para>
|
|
|
|
<sect1><title>Frame Buffer Memory</title>
|
|
!Edrivers/video/fbmem.c
|
|
</sect1>
|
|
<!--
|
|
<sect1><title>Frame Buffer Console</title>
|
|
X!Edrivers/video/console/fbcon.c
|
|
</sect1>
|
|
-->
|
|
<sect1><title>Frame Buffer Colormap</title>
|
|
!Edrivers/video/fbcmap.c
|
|
</sect1>
|
|
<!-- FIXME:
|
|
drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
|
|
out until somebody adds docs. KAO
|
|
<sect1><title>Frame Buffer Generic Functions</title>
|
|
X!Idrivers/video/fbgen.c
|
|
</sect1>
|
|
KAO -->
|
|
<sect1><title>Frame Buffer Video Mode Database</title>
|
|
!Idrivers/video/modedb.c
|
|
!Edrivers/video/modedb.c
|
|
</sect1>
|
|
<sect1><title>Frame Buffer Macintosh Video Mode Database</title>
|
|
!Edrivers/video/macmodes.c
|
|
</sect1>
|
|
<sect1><title>Frame Buffer Fonts</title>
|
|
<para>
|
|
Refer to the file drivers/video/console/fonts.c for more information.
|
|
</para>
|
|
<!-- FIXME: Removed for now since no structured comments in source
|
|
X!Idrivers/video/console/fonts.c
|
|
-->
|
|
</sect1>
|
|
</chapter>
|
|
|
|
<chapter id="input_subsystem">
|
|
<title>Input Subsystem</title>
|
|
!Iinclude/linux/input.h
|
|
!Edrivers/input/input.c
|
|
!Edrivers/input/ff-core.c
|
|
!Edrivers/input/ff-memless.c
|
|
</chapter>
|
|
|
|
<chapter id="spi">
|
|
<title>Serial Peripheral Interface (SPI)</title>
|
|
<para>
|
|
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.
|
|
</para>
|
|
<para>
|
|
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.)
|
|
</para>
|
|
<para>
|
|
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
|
|
<structname>struct spi_master</structname>.
|
|
SPI devices are children of that master, represented as a
|
|
<structname>struct spi_device</structname> and manufactured from
|
|
<structname>struct spi_board_info</structname> descriptors which
|
|
are usually provided by board-specific initialization code.
|
|
A <structname>struct spi_driver</structname> is called a
|
|
"Protocol Driver", and is bound to a spi_device using normal
|
|
driver model calls.
|
|
</para>
|
|
<para>
|
|
The I/O model is a set of queued messages. Protocol drivers
|
|
submit one or more <structname>struct spi_message</structname>
|
|
objects, which are processed and completed asynchronously.
|
|
(There are synchronous wrappers, however.) Messages are
|
|
built from one or more <structname>struct spi_transfer</structname>
|
|
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.
|
|
</para>
|
|
!Iinclude/linux/spi/spi.h
|
|
!Fdrivers/spi/spi.c spi_register_board_info
|
|
!Edrivers/spi/spi.c
|
|
</chapter>
|
|
|
|
</book>
|