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[PATCH] spi: add spi_driver to SPI framework

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This is a refresh of the "Simple SPI Framework" found in 2.6.15-rc3-mm1
which makes the following changes:

  * There's now a "struct spi_driver".  This increase the footprint
    of the core a bit, since it now includes code to do what the driver
    core was previously handling directly.  Documentation and comments
    were updated to match.

  * spi_alloc_master() now does class_device_initialize(), so it can
    at least be refcounted before spi_register_master().  To match,
    spi_register_master() switched over to class_device_add().

  * States explicitly that after transfer errors, spi_devices will be
    deselected.  We want fault recovery procedures to work the same
    for all controller drivers.

  * Minor tweaks:  controller_data no longer points to readonly data;
    prevent some potential cast-from-null bugs with container_of calls;
    clarifies some existing kerneldoc,

And a few small cleanups.

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>
This commit is contained in:
David Brownell
2006-01-08 13:34:23 -08:00
committed by Greg Kroah-Hartman
parent 1d6432fe10
commit b885244eb2
3 changed files with 171 additions and 76 deletions
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52
Documentation/spi/spi-summary
View File

@ -1,18 +1,19 @@
Overview of Linux kernel SPI support
====================================
22-Nov-2005
02-Dec-2005
What is SPI?
------------
The "Serial Peripheral Interface" (SPI) is a four-wire point-to-point
serial link used to connect microcontrollers to sensors and memory.
The "Serial Peripheral Interface" (SPI) is a synchronous four wire serial
link used to connect microcontrollers to sensors, memory, and peripherals.
The three signal wires hold a clock (SCLK, often on the order of 10 MHz),
and parallel data lines with "Master Out, Slave In" (MOSI) or "Master In,
Slave Out" (MISO) signals. (Other names are also used.) There are four
clocking modes through which data is exchanged; mode-0 and mode-3 are most
commonly used.
commonly used. Each clock cycle shifts data out and data in; the clock
doesn't cycle except when there is data to shift.
SPI masters may use a "chip select" line to activate a given SPI slave
device, so those three signal wires may be connected to several chips
@ -79,11 +80,18 @@ The <linux/spi/spi.h> header file includes kerneldoc, as does the
main source code, and you should certainly read that. This is just
an overview, so you get the big picture before the details.
SPI requests always go into I/O queues. Requests for a given SPI device
are always executed in FIFO order, and complete asynchronously through
completion callbacks. There are also some simple synchronous wrappers
for those calls, including ones for common transaction types like writing
a command and then reading its response.
There are two types of SPI driver, here called:
Controller drivers ... these are often built in to System-On-Chip
processors, and often support both Master and Slave roles.
These drivers touch hardware registers and may use DMA.
Or they can be PIO bitbangers, needing just GPIO pins.
Protocol drivers ... these pass messages through the controller
driver to communicate with a Slave or Master device on the
@ -116,11 +124,6 @@ shows up in sysfs in several locations:
managing bus "B". All the spiB.* devices share the same
physical SPI bus segment, with SCLK, MOSI, and MISO.
The basic I/O primitive submits an asynchronous message to an I/O queue
maintained by the controller driver. A completion callback is issued
asynchronously when the data transfer(s) in that message completes.
There are also some simple synchronous wrappers for those calls.
How does board-specific init code declare SPI devices?
------------------------------------------------------
@ -263,33 +266,40 @@ would just be another kernel driver, probably offering some lowlevel
access through aio_read(), aio_write(), and ioctl() calls and using the
standard userspace sysfs mechanisms to bind to a given SPI device.
SPI protocol drivers are normal device drivers, with no more wrapper
than needed by platform devices:
SPI protocol drivers somewhat resemble platform device drivers:
static struct spi_driver CHIP_driver = {
.driver = {
.name = "CHIP",
.bus = &spi_bus_type,
.owner = THIS_MODULE,
},
static struct device_driver CHIP_driver = {
.name = "CHIP",
.bus = &spi_bus_type,
.probe = CHIP_probe,
.remove = __exit_p(CHIP_remove),
.remove = __devexit_p(CHIP_remove),
.suspend = CHIP_suspend,
.resume = CHIP_resume,
};
The SPI core will autmatically attempt to bind this driver to any SPI
The driver core will autmatically attempt to bind this driver to any SPI
device whose board_info gave a modalias of "CHIP". Your probe() code
might look like this unless you're creating a class_device:
static int __init CHIP_probe(struct device *dev)
static int __devinit CHIP_probe(struct spi_device *spi)
{
struct spi_device *spi = to_spi_device(dev);
struct CHIP *chip;
struct CHIP_platform_data *pdata = dev->platform_data;
struct CHIP_platform_data *pdata;
/* assuming the driver requires board-specific data: */
pdata = &spi->dev.platform_data;
if (!pdata)
return -ENODEV;
/* get memory for driver's per-chip state */
chip = kzalloc(sizeof *chip, GFP_KERNEL);
if (!chip)
return -ENOMEM;
dev_set_drvdata(dev, chip);
dev_set_drvdata(&spi->dev, chip);
... etc
return 0;
@ -328,6 +338,8 @@ the driver guarantees that it won't submit any more such messages.
- The basic I/O primitive is spi_async(). Async requests may be
issued in any context (irq handler, task, etc) and completion
is reported using a callback provided with the message.
After any detected error, the chip is deselected and processing
of that spi_message is aborted.
- There are also synchronous wrappers like spi_sync(), and wrappers
like spi_read(), spi_write(), and spi_write_then_read(). These