Commit 8ae12a0d authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman

[PATCH] spi: simple SPI framework

This is the core of a small SPI framework, implementing the model of a
queue of messages which complete asynchronously (with thin synchronous
wrappers on top).

  - It's still less than 2KB of ".text" (ARM).  If there's got to be a
    mid-layer for something so simple, that's the right size budget.  :)

  - The guts use board-specific SPI device tables to build the driver
    model tree.  (Hardware probing is rarely an option.)

  - This version of Kconfig includes no drivers.  At this writing there
    are two known master controller drivers (PXA/SSP, OMAP MicroWire)
    and three protocol drivers (CS8415a, ADS7846, DataFlash) with LKML
    mentions of other drivers in development.

  - No userspace API.  There are several implementations to compare.
    Implement them like any other driver, and bind them with sysfs.

The changes from last version posted to LKML (on 11-Nov-2005) are minor,
and include:

  - One bugfix (removes a FIXME), with the visible effect of making device
    names be "spiB.C" where B is the bus number and C is the chipselect.

  - The "caller provides DMA mappings" mechanism now has kerneldoc, for
    DMA drivers that want to be fancy.

  - Hey, the framework init can be subsys_init.  Even though board init
    logic fires earlier, at arch_init ... since the framework init is
    for driver support, and the board init support uses static init.

  - Various additional spec/doc clarifications based on discussions
    with other folk.  It adds a brief "thank you" at the end, for folk
    who've helped nudge this framework into existence.

As I've said before, I think that "protocol tweaking" is the main support
that this driver framework will need to evolve.

From: Mark Underwood <basicmark@yahoo.com>

  Update the SPI framework to remove a potential priority inversion case by
  reverting to kmalloc if the pre-allocated DMA-safe buffer isn't available.
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 67daf5f1
This diff is collapsed.
......@@ -729,6 +729,8 @@ source "drivers/char/Kconfig"
source "drivers/i2c/Kconfig"
source "drivers/spi/Kconfig"
source "drivers/hwmon/Kconfig"
#source "drivers/l3/Kconfig"
......
......@@ -44,6 +44,8 @@ source "drivers/char/Kconfig"
source "drivers/i2c/Kconfig"
source "drivers/spi/Kconfig"
source "drivers/w1/Kconfig"
source "drivers/hwmon/Kconfig"
......
......@@ -41,6 +41,7 @@ obj-$(CONFIG_FUSION) += message/
obj-$(CONFIG_IEEE1394) += ieee1394/
obj-y += cdrom/
obj-$(CONFIG_MTD) += mtd/
obj-$(CONFIG_SPI) += spi/
obj-$(CONFIG_PCCARD) += pcmcia/
obj-$(CONFIG_DIO) += dio/
obj-$(CONFIG_SBUS) += sbus/
......
#
# SPI driver configuration
#
# NOTE: the reason this doesn't show SPI slave support is mostly that
# nobody's needed a slave side API yet. The master-role API is not
# fully appropriate there, so it'd need some thought to do well.
#
menu "SPI support"
config SPI
bool "SPI support"
help
The "Serial Peripheral Interface" is a low level synchronous
protocol. Chips that support SPI can have data transfer rates
up to several tens of Mbit/sec. Chips are addressed with a
controller and a chipselect. Most SPI slaves don't support
dynamic device discovery; some are even write-only or read-only.
SPI is widely used by microcontollers to talk with sensors,
eeprom and flash memory, codecs and various other controller
chips, analog to digital (and d-to-a) converters, and more.
MMC and SD cards can be accessed using SPI protocol; and for
DataFlash cards used in MMC sockets, SPI must always be used.
SPI is one of a family of similar protocols using a four wire
interface (select, clock, data in, data out) including Microwire
(half duplex), SSP, SSI, and PSP. This driver framework should
work with most such devices and controllers.
config SPI_DEBUG
boolean "Debug support for SPI drivers"
depends on SPI && DEBUG_KERNEL
help
Say "yes" to enable debug messaging (like dev_dbg and pr_debug),
sysfs, and debugfs support in SPI controller and protocol drivers.
#
# MASTER side ... talking to discrete SPI slave chips including microcontrollers
#
config SPI_MASTER
# boolean "SPI Master Support"
boolean
default SPI
help
If your system has an master-capable SPI controller (which
provides the clock and chipselect), you can enable that
controller and the protocol drivers for the SPI slave chips
that are connected.
comment "SPI Master Controller Drivers"
depends on SPI_MASTER
#
# Add new SPI master controllers in alphabetical order above this line
#
#
# There are lots of SPI device types, with sensors and memory
# being probably the most widely used ones.
#
comment "SPI Protocol Masters"
depends on SPI_MASTER
#
# Add new SPI protocol masters in alphabetical order above this line
#
# (slave support would go here)
endmenu # "SPI support"
#
# Makefile for kernel SPI drivers.
#
ifeq ($(CONFIG_SPI_DEBUG),y)
EXTRA_CFLAGS += -DDEBUG
endif
# small core, mostly translating board-specific
# config declarations into driver model code
obj-$(CONFIG_SPI_MASTER) += spi.o
# SPI master controller drivers (bus)
# ... add above this line ...
# SPI protocol drivers (device/link on bus)
# ... add above this line ...
# SPI slave controller drivers (upstream link)
# ... add above this line ...
# SPI slave drivers (protocol for that link)
# ... add above this line ...
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