* @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).
* @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;
#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
#define SPI_CS_HIGH 0x04 /* chipselect active high? */
#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
+#define SPI_3WIRE 0x10 /* SI/SO signals shared */
u8 bits_per_word;
int irq;
void *controller_state;
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)
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)
* @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 {
* 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;
* 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
*
* 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
* chip transactions together.
*
* (ii) When the transfer is the last one in the message, the chip may
- * stay selected until the next transfer. This is purely a performance
- * hint; the controller driver may need to select a different device
- * for the next message.
+ * stay selected until the next transfer. On multi-device SPI busses
+ * with nothing blocking messages going to other devices, this is just
+ * a performance hint; starting a message to another device deselects
+ * this one. But in other cases, this can be used to ensure correctness.
+ * Some devices need protocol transactions to be built from a series of
+ * spi_message submissions, where the content of one message is determined
+ * by the results of previous messages and where the whole transaction
+ * ends when the chipselect goes intactive.
*
* The code that submits an spi_message (and its spi_transfers)
* to the lower layers is responsible for managing its memory.
* @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
}
/**
- * 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, and no requests are queued to the device
*
* 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
+ * device doesn't work with its default. They may likewise need
* to update clock rates or word sizes from initial values. This function
* changes those settings, and must be called from a context that can sleep.
- * The changes take effect the next time the device is selected and data
- * is transferred to or from it.
+ * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
+ * effect the next time the device is selected and data is transferred to
+ * or from it. When this function returns, the spi device is deselected.
*
- * 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.
/**
- * 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.
* @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.
* @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
* 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
* 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
projects / linux-2.6-omap-h63xx.git / blobdiff