SPI kerneldoc

Various documentation updates for the SPI infrastructure, to clarify things
that may not have been clear, to cope with lack of editing, and fix
omissions.

Also, plug SPI into the kernel-api DocBook template, and fix all the
resulting glitches in document generation.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 51 insertions, 31 deletions

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 4f0f8c2e58a..b6bedc3ee95 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -32,11 +32,12 @@ extern struct bus_type spi_bus_type;
  * @max_speed_hz: Maximum clock rate to be used with this chip
  *	(on this board); may be changed by the device's driver.
  *	The spi_transfer.speed_hz can override this for each transfer.
- * @chip-select: Chipselect, distinguishing chips handled by "master".
+ * @chip_select: Chipselect, distinguishing chips handled by @master.
  * @mode: The spi mode defines how data is clocked out and in.
  *	This may be changed by the device's driver.
- *	The "active low" default for chipselect mode can be overridden,
- *	as can the "MSB first" default for each word in a transfer.
+ *	The "active low" default for chipselect mode can be overridden
+ *	(by specifying SPI_CS_HIGH) as can the "MSB first" default for
+ *	each word in a transfer (by specifying SPI_LSB_FIRST).
  * @bits_per_word: Data transfers involve one or more words; word sizes
  *	like eight or 12 bits are common.  In-memory wordsizes are
  *	powers of two bytes (e.g. 20 bit samples use 32 bits).
@@ -48,14 +49,18 @@ extern struct bus_type spi_bus_type;
  * @controller_state: Controller's runtime state
  * @controller_data: Board-specific definitions for controller, such as
  *	FIFO initialization parameters; from board_info.controller_data
+ * @modalias: Name of the driver to use with this device, or an alias
+ *	for that name.  This appears in the sysfs "modalias" attribute
+ *	for driver coldplugging, and in uevents used for hotplugging
  *
- * An spi_device is used to interchange data between an SPI slave
+ * A @spi_device is used to interchange data between an SPI slave
  * (usually a discrete chip) and CPU memory.
  *
- * In "dev", the platform_data is used to hold information about this
+ * In @dev, the platform_data is used to hold information about this
  * device that's meaningful to the device's protocol driver, but not
  * to its controller.  One example might be an identifier for a chip
- * variant with slightly different functionality.
+ * variant with slightly different functionality; another might be
+ * information about how this particular board wires the chip's pins.
  */
 struct spi_device {
 	struct device		dev;
@@ -77,13 +82,15 @@ struct spi_device {
 	void			*controller_data;
 	const char		*modalias;
 
-	// likely need more hooks for more protocol options affecting how
-	// the controller talks to each chip, like:
-	//  - memory packing (12 bit samples into low bits, others zeroed)
-	//  - priority
-	//  - drop chipselect after each word
-	//  - chipselect delays
-	//  - ...
+	/*
+	 * likely need more hooks for more protocol options affecting how
+	 * the controller talks to each chip, like:
+	 *  - memory packing (12 bit samples into low bits, others zeroed)
+	 *  - priority
+	 *  - drop chipselect after each word
+	 *  - chipselect delays
+	 *  - ...
+	 */
 };
 
 static inline struct spi_device *to_spi_device(struct device *dev)
@@ -146,6 +153,11 @@ static inline struct spi_driver *to_spi_driver(struct device_driver *drv)
 
 extern int spi_register_driver(struct spi_driver *sdrv);
 
+/**
+ * spi_unregister_driver - reverse effect of spi_register_driver
+ * @sdrv: the driver to unregister
+ * Context: can sleep
+ */
 static inline void spi_unregister_driver(struct spi_driver *sdrv)
 {
 	if (sdrv)
@@ -165,18 +177,20 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  * @setup: updates the device mode and clocking records used by a
  *	device's SPI controller; protocol code may call this.  This
  *	must fail if an unrecognized or unsupported mode is requested.
+ *	It's always safe to call this unless transfers are pending on
+ *	the device whose settings are being modified.
  * @transfer: adds a message to the controller's transfer queue.
  * @cleanup: frees controller-specific state
  *
- * Each SPI master controller can communicate with one or more spi_device
+ * Each SPI master controller can communicate with one or more @spi_device
  * children.  These make a small bus, sharing MOSI, MISO and SCK signals
  * but not chip select signals.  Each device may be configured to use a
  * different clock rate, since those shared signals are ignored unless
  * the chip is selected.
  *
  * The driver for an SPI controller manages access to those devices through
- * a queue of spi_message transactions, copyin data between CPU memory and
- * an SPI slave device).  For each such message it queues, it calls the
+ * a queue of spi_message transactions, copying data between CPU memory and
+ * an SPI slave device.  For each such message it queues, it calls the
  * message's completion function when the transaction completes.
  */
 struct spi_master {
@@ -280,27 +294,27 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
  * struct spi_transfer - a read/write buffer pair
  * @tx_buf: data to be written (dma-safe memory), or NULL
  * @rx_buf: data to be read (dma-safe memory), or NULL
- * @tx_dma: DMA address of tx_buf, if spi_message.is_dma_mapped
- * @rx_dma: DMA address of rx_buf, if spi_message.is_dma_mapped
+ * @tx_dma: DMA address of tx_buf, if @spi_message.is_dma_mapped
+ * @rx_dma: DMA address of rx_buf, if @spi_message.is_dma_mapped
  * @len: size of rx and tx buffers (in bytes)
  * @speed_hz: Select a speed other then the device default for this
- *      transfer. If 0 the default (from spi_device) is used.
+ *      transfer. If 0 the default (from @spi_device) is used.
  * @bits_per_word: select a bits_per_word other then the device default
- *      for this transfer. If 0 the default (from spi_device) is used.
+ *      for this transfer. If 0 the default (from @spi_device) is used.
  * @cs_change: affects chipselect after this transfer completes
  * @delay_usecs: microseconds to delay after this transfer before
  *	(optionally) changing the chipselect status, then starting
- *	the next transfer or completing this spi_message.
- * @transfer_list: transfers are sequenced through spi_message.transfers
+ *	the next transfer or completing this @spi_message.
+ * @transfer_list: transfers are sequenced through @spi_message.transfers
  *
  * SPI transfers always write the same number of bytes as they read.
- * Protocol drivers should always provide rx_buf and/or tx_buf.
+ * Protocol drivers should always provide @rx_buf and/or @tx_buf.
  * In some cases, they may also want to provide DMA addresses for
  * the data being transferred; that may reduce overhead, when the
  * underlying driver uses dma.
  *
  * If the transmit buffer is null, zeroes will be shifted out
- * while filling rx_buf.  If the receive buffer is null, the data
+ * while filling @rx_buf.  If the receive buffer is null, the data
  * shifted in will be discarded.  Only "len" bytes shift out (or in).
  * It's an error to try to shift out a partial word.  (For example, by
  * shifting out three bytes with word size of sixteen or twenty bits;
@@ -309,7 +323,7 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
  * In-memory data values are always in native CPU byte order, translated
  * from the wire byte order (big-endian except with SPI_LSB_FIRST).  So
  * for example when bits_per_word is sixteen, buffers are 2N bytes long
- * and hold N sixteen bit words in CPU byte order.
+ * (@len = 2N) and hold N sixteen bit words in CPU byte order.
  *
  * When the word size of the SPI transfer is not a power-of-two multiple
  * of eight bits, those in-memory words include extra bits.  In-memory
@@ -318,7 +332,7 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
  *
  * All SPI transfers start with the relevant chipselect active.  Normally
  * it stays selected until after the last transfer in a message.  Drivers
- * can affect the chipselect signal using cs_change:
+ * can affect the chipselect signal using cs_change.
  *
  * (i) If the transfer isn't the last one in the message, this flag is
  * used to make the chipselect briefly go inactive in the middle of the
@@ -372,7 +386,7 @@ struct spi_transfer {
  * @queue: for use by whichever driver currently owns the message
  * @state: for use by whichever driver currently owns the message
  *
- * An spi_message is used to execute an atomic sequence of data transfers,
+ * A @spi_message is used to execute an atomic sequence of data transfers,
  * each represented by a struct spi_transfer.  The sequence is "atomic"
  * in the sense that no other spi_message may use that SPI bus until that
  * sequence completes.  On some systems, many such sequences can execute as
@@ -464,8 +478,9 @@ static inline void spi_message_free(struct spi_message *m)
 }
 
 /**
- * spi_setup -- setup SPI mode and clock rate
+ * spi_setup - setup SPI mode and clock rate
  * @spi: the device whose settings are being modified
+ * Context: can sleep
  *
  * SPI protocol drivers may need to update the transfer mode if the
  * device doesn't work with the mode 0 default.  They may likewise need
@@ -474,7 +489,7 @@ static inline void spi_message_free(struct spi_message *m)
  * The changes take effect the next time the device is selected and data
  * is transferred to or from it.
  *
- * Note that this call wil fail if the protocol driver specifies an option
+ * Note that this call will fail if the protocol driver specifies an option
  * that the underlying controller or its driver does not support.  For
  * example, not all hardware supports wire transfers using nine bit words,
  * LSB-first wire encoding, or active-high chipselects.
@@ -487,9 +502,10 @@ spi_setup(struct spi_device *spi)
 
 
 /**
- * spi_async -- asynchronous SPI transfer
+ * spi_async - asynchronous SPI transfer
  * @spi: device with which data will be exchanged
  * @message: describes the data transfers, including completion callback
+ * Context: any (irqs may be blocked, etc)
  *
  * This call may be used in_irq and other contexts which can't sleep,
  * as well as from task contexts which can sleep.
@@ -535,6 +551,7 @@ extern int spi_sync(struct spi_device *spi, struct spi_message *message);
  * @spi: device to which data will be written
  * @buf: data buffer
  * @len: data buffer size
+ * Context: can sleep
  *
  * This writes the buffer and returns zero or a negative error code.
  * Callable only from contexts that can sleep.
@@ -558,8 +575,9 @@ spi_write(struct spi_device *spi, const u8 *buf, size_t len)
  * @spi: device from which data will be read
  * @buf: data buffer
  * @len: data buffer size
+ * Context: can sleep
  *
- * This writes the buffer and returns zero or a negative error code.
+ * This reads the buffer and returns zero or a negative error code.
  * Callable only from contexts that can sleep.
  */
 static inline int
@@ -585,6 +603,7 @@ extern int spi_write_then_read(struct spi_device *spi,
  * spi_w8r8 - SPI synchronous 8 bit write followed by 8 bit read
  * @spi: device with which data will be exchanged
  * @cmd: command to be written before data is read back
+ * Context: can sleep
  *
  * This returns the (unsigned) eight bit number returned by the
  * device, or else a negative error code.  Callable only from
@@ -605,6 +624,7 @@ static inline ssize_t spi_w8r8(struct spi_device *spi, u8 cmd)
  * spi_w8r16 - SPI synchronous 8 bit write followed by 16 bit read
  * @spi: device with which data will be exchanged
  * @cmd: command to be written before data is read back
+ * Context: can sleep
  *
  * This returns the (unsigned) sixteen bit number returned by the
  * device, or else a negative error code.  Callable only from