path: root/Documentation/spi
diff options
authorDavid Brownell <dbrownell@users.sourceforge.net>2009-06-30 18:41:26 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-01 01:56:00 (GMT)
commitb55f627feeb9d48fdbde3835e18afbc76712e49b (patch)
tree1c6084d44f23c5e70040e5d62c93718f77ad09da /Documentation/spi
parentc49568235dd7b4a2ffad63aa950562f4ffb9455f (diff)
spi: new spi->mode bits
Add two new spi_device.mode bits to accomodate more protocol options, and pass them through to usermode drivers: * SPI_NO_CS ... a second 3-wire variant, where the chipselect line is removed instead of a data line; transfers are still full duplex. This obviously has STRONG protocol implications since the chipselect transitions can't be used to synchronize state transitions with the SPI master. * SPI_READY ... defines open drain signal that's pulled low to pause the clock. This defines a 5-wire variant (normal 4-wire SPI plus READY) and two 4-wire variants (READY plus each of the 3-wire flavors). Such hardware flow control can be a big win. There are ADC converters and flash chips that expose READY signals, but not many host controllers support it today. The spi_bitbang code should be changed to use SPI_NO_CS instead of its current nonportable hack. That's a mode most hardware can easily support (unlike SPI_READY). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: "Paulraj, Sandeep" <s-paulraj@ti.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/spi')
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/spi/spidev_test.c b/Documentation/spi/spidev_test.c
index cf0e3ce0..c1a5aad 100644
--- a/Documentation/spi/spidev_test.c
+++ b/Documentation/spi/spidev_test.c
@@ -99,11 +99,13 @@ void parse_opts(int argc, char *argv[])
{ "lsb", 0, 0, 'L' },
{ "cs-high", 0, 0, 'C' },
{ "3wire", 0, 0, '3' },
+ { "no-cs", 0, 0, 'N' },
+ { "ready", 0, 0, 'R' },
{ NULL, 0, 0, 0 },
int c;
- c = getopt_long(argc, argv, "D:s:d:b:lHOLC3", lopts, NULL);
+ c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
if (c == -1)
@@ -139,6 +141,12 @@ void parse_opts(int argc, char *argv[])
case '3':
mode |= SPI_3WIRE;
+ case 'N':
+ mode |= SPI_NO_CS;
+ break;
+ case 'R':
+ mode |= SPI_READY;
+ break;

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