[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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
new file mode 100644
index 0000000..d310510
--- /dev/null
+++ b/drivers/spi/Kconfig
@@ -0,0 +1,76 @@
+#
+# 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"
+