8ae12a0d85
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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
77 lines
2.2 KiB
Plaintext
77 lines
2.2 KiB
Plaintext
#
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# SPI driver configuration
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#
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# NOTE: the reason this doesn't show SPI slave support is mostly that
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# nobody's needed a slave side API yet. The master-role API is not
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# fully appropriate there, so it'd need some thought to do well.
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#
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menu "SPI support"
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config SPI
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bool "SPI support"
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help
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The "Serial Peripheral Interface" is a low level synchronous
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protocol. Chips that support SPI can have data transfer rates
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up to several tens of Mbit/sec. Chips are addressed with a
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controller and a chipselect. Most SPI slaves don't support
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dynamic device discovery; some are even write-only or read-only.
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SPI is widely used by microcontollers to talk with sensors,
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eeprom and flash memory, codecs and various other controller
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chips, analog to digital (and d-to-a) converters, and more.
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MMC and SD cards can be accessed using SPI protocol; and for
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DataFlash cards used in MMC sockets, SPI must always be used.
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SPI is one of a family of similar protocols using a four wire
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interface (select, clock, data in, data out) including Microwire
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(half duplex), SSP, SSI, and PSP. This driver framework should
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work with most such devices and controllers.
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config SPI_DEBUG
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boolean "Debug support for SPI drivers"
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depends on SPI && DEBUG_KERNEL
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help
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Say "yes" to enable debug messaging (like dev_dbg and pr_debug),
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sysfs, and debugfs support in SPI controller and protocol drivers.
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#
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# MASTER side ... talking to discrete SPI slave chips including microcontrollers
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#
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config SPI_MASTER
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# boolean "SPI Master Support"
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boolean
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default SPI
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help
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If your system has an master-capable SPI controller (which
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provides the clock and chipselect), you can enable that
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controller and the protocol drivers for the SPI slave chips
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that are connected.
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comment "SPI Master Controller Drivers"
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depends on SPI_MASTER
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#
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# Add new SPI master controllers in alphabetical order above this line
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#
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#
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# There are lots of SPI device types, with sensors and memory
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# being probably the most widely used ones.
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#
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comment "SPI Protocol Masters"
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depends on SPI_MASTER
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#
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# Add new SPI protocol masters in alphabetical order above this line
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#
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# (slave support would go here)
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endmenu # "SPI support"
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