From b55f627feeb9d48fdbde3835e18afbc76712e49b Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 30 Jun 2009 11:41:26 -0700 Subject: 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 Cc: "Paulraj, Sandeep" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/spi/spidev_test.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'Documentation/spi') diff --git a/Documentation/spi/spidev_test.c b/Documentation/spi/spidev_test.c index cf0e3ce0d526..c1a5aad3c75a 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) break; @@ -139,6 +141,12 @@ void parse_opts(int argc, char *argv[]) case '3': mode |= SPI_3WIRE; break; + case 'N': + mode |= SPI_NO_CS; + break; + case 'R': + mode |= SPI_READY; + break; default: print_usage(argv[0]); break; -- cgit v1.2.3