The patch
spi: Document SPI slave controller support
has been applied to the spi tree at
git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git
All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.
You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.
If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
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Please add any relevant lists and maintainers to the CCs when replying
to this mail.
Thanks,
Mark
>From aa2ea9115bc3f0735aa65b833076cc5fe3da1489 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Date: Mon, 22 May 2017 15:11:42 +0200
Subject: [PATCH] spi: Document SPI slave controller support
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
Documentation/spi/spi-summary | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary
index d1824b399b2d..1721c1b570c3 100644
--- a/Documentation/spi/spi-summary
+++ b/Documentation/spi/spi-summary
@@ -62,8 +62,8 @@ chips described as using "three wire" signaling: SCK, data, nCSx.
(That data line is sometimes called MOMI or SISO.)
Microcontrollers often support both master and slave sides of the SPI
-protocol. This document (and Linux) currently only supports the master
-side of SPI interactions.
+protocol. This document (and Linux) supports both the master and slave
+sides of SPI interactions.
Who uses it? On what kinds of systems?
@@ -154,9 +154,8 @@ control audio interfaces, present touchscreen sensors as input interfaces,
or monitor temperature and voltage levels during industrial processing.
And those might all be sharing the same controller driver.
-A "struct spi_device" encapsulates the master-side interface between
-those two types of driver. At this writing, Linux has no slave side
-programming interface.
+A "struct spi_device" encapsulates the controller-side interface between
+those two types of drivers.
There is a minimal core of SPI programming interfaces, focussing on
using the driver model to connect controller and protocol drivers using
@@ -177,10 +176,24 @@ shows up in sysfs in several locations:
/sys/bus/spi/drivers/D ... driver for one or more spi*.* devices
/sys/class/spi_master/spiB ... symlink (or actual device node) to
- a logical node which could hold class related state for the
- controller managing bus "B". All spiB.* devices share one
+ a logical node which could hold class related state for the SPI
+ master controller managing bus "B". All spiB.* devices share one
physical SPI bus segment, with SCLK, MOSI, and MISO.
+ /sys/devices/.../CTLR/slave ... virtual file for (un)registering the
+ slave device for an SPI slave controller.
+ Writing the driver name of an SPI slave handler to this file
+ registers the slave device; writing "(null)" unregisters the slave
+ device.
+ Reading from this file shows the name of the slave device ("(null)"
+ if not registered).
+
+ /sys/class/spi_slave/spiB ... symlink (or actual device node) to
+ a logical node which could hold class related state for the SPI
+ slave controller on bus "B". When registered, a single spiB.*
+ device is present here, possible sharing the physical SPI bus
+ segment with other SPI slave devices.
+
Note that the actual location of the controller's class state depends
on whether you enabled CONFIG_SYSFS_DEPRECATED or not. At this time,
the only class-specific state is the bus number ("B" in "spiB"), so
--
2.11.0
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