spi: documentation: emphasise spi_master.setup() semantics

[net-next-2.6.git] / Documentation / spi / spi-summary

diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary
index 0f5122eb282bad1616b4bff089af95ac35e33a1f..4a02d2508bc8b951402bf9ab74411f16da1e1b52 100644 (file)
--- a/Documentation/spi/spi-summary
+++ b/Documentation/spi/spi-summary
@@ -511,10 +511,16 @@ SPI MASTER METHODS
        This sets up the device clock rate, SPI mode, and word sizes.
        Drivers may change the defaults provided by board_info, and then
        call spi_setup(spi) to invoke this routine.  It may sleep.
+
        Unless each SPI slave has its own configuration registers, don't
        change them right away ... otherwise drivers could corrupt I/O
        that's in progress for other SPI devices.
 
+               ** BUG ALERT:  for some reason the first version of
+               ** many spi_master drivers seems to get this wrong.
+               ** When you code setup(), ASSUME that the controller
+               ** is actively processing transfers for another device.
+
     master->transfer(struct spi_device *spi, struct spi_message *message)
        This must not sleep.  Its responsibility is arrange that the
        transfer happens and its complete() callback is issued.  The two