The patch titled spi: documentation tweaks has been removed from the -mm tree. Its filename was spi-documentation-tweaks.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: spi: documentation tweaks From: David Brownell <david-b@xxxxxxxxxxx> Update SPI documentation to clarify some areas of recent confusion: clock polarity takes effect when chipselect goes active; and zero length buffers are OK in certain cases. Signed-off-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/spi/spi-summary | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff -puN Documentation/spi/spi-summary~spi-documentation-tweaks Documentation/spi/spi-summary --- a/Documentation/spi/spi-summary~spi-documentation-tweaks +++ a/Documentation/spi/spi-summary @@ -116,6 +116,13 @@ low order bit. So when a chip's timing starting low (CPOL=0) and data stabilized for sampling during the trailing clock edge (CPHA=1), that's SPI mode 1. +Note that the clock mode is relevant as soon as the chipselect goes +active. So the master must set the clock to inactive before selecting +a slave, and the slave can tell the chosen polarity by sampling the +clock level when its select line goes active. That's why many devices +support for example both modes 0 and 3: they don't care about polarity, +and alway clock data in/out on rising clock edges. + How do these driver programming interfaces work? ------------------------------------------------ @@ -379,8 +386,14 @@ any more such messages. + when bidirectional reads and writes start ... by how its sequence of spi_transfer requests is arranged; + + which I/O buffers are used ... each spi_transfer wraps a + buffer for each transfer direction, supporting full duplex + (two pointers, maybe the same one in both cases) and half + duplex (one pointer is NULL) transfers; + + optionally defining short delays after transfers ... using - the spi_transfer.delay_usecs setting; + the spi_transfer.delay_usecs setting (this delay can be the + only protocol effect, if the buffer length is zero); + whether the chipselect becomes inactive after a transfer and any delay ... by using the spi_transfer.cs_change flag; _ Patches currently in -mm which might be from david-b@xxxxxxxxxxx are origin.patch git-acpi.patch git-arm.patch git-avr32.patch pm-introduce-new-top-level-suspend-and-hibernation-callbacks-rev-7.patch pm-introduce-new-top-level-suspend-and-hibernation-callbacks-rev-7-fix.patch pm-new-suspend-and-hibernation-callbacks-for-platform-bus-type-rev-3.patch pm-new-suspend-and-hibernation-callbacks-for-pci-bus-type-rev-3.patch git-input.patch input-add-debouncing-for-generic-gpio-input-device-gpio_keyc.patch jffs2-summary-allocation-dont-use-vmalloc.patch fix-gregkh-usb-usb-ohci-port-reset-paranoia-timeout.patch spi-pxa2xx_spi-sparse-fixes.patch atmel_spi-support-zero-length-transfer.patch rtc-avoid-legacy-drivers-with-generic-framework.patch rtc-avoid-legacy-drivers-with-generic-framework-update.patch rtc-isl1208-new-style-conversion-and-minor-bug-fixes.patch rtc-isl1208-new-style-conversion-and-minor-bug-fixes-checkpatch-fixes.patch rtc-pcf8563-new-style-conversion.patch rtc-pcf8563-new-style-conversion-checkpatch-fixes.patch rtc-pcf8563-new-style-conversion-checkpatch-fixes-fix.patch rtc-x1205-new-style-conversion.patch rtc-x1205-new-style-conversion-checkpatch-fixes.patch rtc-silence-section-mismatch-warning-in-rtc-test.patch make-ds1511_rtc_readset_time-static.patch kerneldoc-for-linux-clkh.patch kerneldoc-for-linux-clkh-fix.patch rtc-rtc-rs5c372-fix-up-null-name-in-transfer-error-path.patch rtc-rtc-rs5c372-smbus-conversion-support.patch rtc-rtc-rs5c732-add-support-for-ricoh-r2025s-d-rtc.patch rtc-replace-remaining-__function__-occurrences.patch gpiochip_reserve-fix-2.patch remove-duplicated-unlikely-in-is_err.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html