1 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 68bb1c501d0d..a0faa18f7b1b 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -204,6 +204,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
  *      SPI slaves, and are numbered from zero to num_chipselects.
  *      each slave has a chipselect signal, but it's common that not
  *      every chipselect is connected to a slave.
+ * @dma_alignment: SPI controller constraint on DMA buffers alignment.
  * @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.
@@ -239,7 +240,17 @@ struct spi_master {
          */
         u16                     num_chipselect;
 
-        /* setup mode and clock, etc (spi driver may call many times) */
+        /* some SPI controllers pose alignment requirements on DMAable
+         * buffers; let protocol drivers know about these requirements.
+         */
+        u16                     dma_alignment;
+
+        /* Setup mode and clock, etc (spi driver may call many times).
+         *
+         * IMPORTANT:  this may be called when transfers to another
+         * device are active.  DO NOT UPDATE SHARED REGISTERS in ways
+         * which could break those transfers.
+         */
         int                     (*setup)(struct spi_device *spi);
 
         /* bidirectional bulk transfers