[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>

1 files changed, 76 insertions, 0 deletions

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
new file mode 100644
index 000000000000..d3105104a297
--- /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"
+