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-rw-r--r--include/linux/spi/spi.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 9d8d63109a8f..4f0f8c2e58a5 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -163,7 +163,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
163 * each slave has a chipselect signal, but it's common that not 163 * each slave has a chipselect signal, but it's common that not
164 * every chipselect is connected to a slave. 164 * every chipselect is connected to a slave.
165 * @setup: updates the device mode and clocking records used by a 165 * @setup: updates the device mode and clocking records used by a
166 * device's SPI controller; protocol code may call this. 166 * device's SPI controller; protocol code may call this. This
167 * must fail if an unrecognized or unsupported mode is requested.
167 * @transfer: adds a message to the controller's transfer queue. 168 * @transfer: adds a message to the controller's transfer queue.
168 * @cleanup: frees controller-specific state 169 * @cleanup: frees controller-specific state
169 * 170 *
@@ -305,6 +306,16 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
305 * shifting out three bytes with word size of sixteen or twenty bits; 306 * shifting out three bytes with word size of sixteen or twenty bits;
306 * the former uses two bytes per word, the latter uses four bytes.) 307 * the former uses two bytes per word, the latter uses four bytes.)
307 * 308 *
309 * In-memory data values are always in native CPU byte order, translated
310 * from the wire byte order (big-endian except with SPI_LSB_FIRST). So
311 * for example when bits_per_word is sixteen, buffers are 2N bytes long
312 * and hold N sixteen bit words in CPU byte order.
313 *
314 * When the word size of the SPI transfer is not a power-of-two multiple
315 * of eight bits, those in-memory words include extra bits. In-memory
316 * words are always seen by protocol drivers as right-justified, so the
317 * undefined (rx) or unused (tx) bits are always the most significant bits.
318 *
308 * All SPI transfers start with the relevant chipselect active. Normally 319 * All SPI transfers start with the relevant chipselect active. Normally
309 * it stays selected until after the last transfer in a message. Drivers 320 * it stays selected until after the last transfer in a message. Drivers
310 * can affect the chipselect signal using cs_change: 321 * can affect the chipselect signal using cs_change:
@@ -462,6 +473,11 @@ static inline void spi_message_free(struct spi_message *m)
462 * changes those settings, and must be called from a context that can sleep. 473 * changes those settings, and must be called from a context that can sleep.
463 * The changes take effect the next time the device is selected and data 474 * The changes take effect the next time the device is selected and data
464 * is transferred to or from it. 475 * is transferred to or from it.
476 *
477 * Note that this call wil fail if the protocol driver specifies an option
478 * that the underlying controller or its driver does not support. For
479 * example, not all hardware supports wire transfers using nine bit words,
480 * LSB-first wire encoding, or active-high chipselects.
465 */ 481 */
466static inline int 482static inline int
467spi_setup(struct spi_device *spi) 483spi_setup(struct spi_device *spi)