[PATCH] SPI: devices can require LSB-first encodings
Add spi_device hook for LSB-first word encoding, and update all the
(in-tree) controller drivers to reject such devices. Eventually,
some controller drivers will be updated to support lsb-first encodings
on the wire; no current drivers need this.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 6c3da64..0f7f5c6 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -187,13 +187,22 @@
if (!spi->max_speed_hz)
return -EINVAL;
+ bitbang = spi_master_get_devdata(spi->master);
+
+ /* REVISIT: some systems will want to support devices using lsb-first
+ * bit encodings on the wire. In pure software that would be trivial,
+ * just bitbang_txrx_le_cphaX() routines shifting the other way, and
+ * some hardware controllers also have this support.
+ */
+ if ((spi->mode & SPI_LSB_FIRST) != 0)
+ return -EINVAL;
+
if (!cs) {
cs = kzalloc(sizeof *cs, SLAB_KERNEL);
if (!cs)
return -ENOMEM;
spi->controller_state = cs;
}
- bitbang = spi_master_get_devdata(spi->master);
if (!spi->bits_per_word)
spi->bits_per_word = 8;