On 26/02/2019 11:54, Peter Rosin wrote:
On 2019-02-25 16:51, Robert Shearman wrote:
From: Robert Shearman <robert.shearman@xxxxxxx>
The behaviour, by default, to not deselect after each transfer is
unsafe when there is a device with an address that conflicts with
another device on another pca954x mux on the same parent bus, and it
may not be convenient to use devicetree to set the deselect mux,
e.g. when running on x86_64 when ACPI is used to discover most of the
device hierarchy.
Therefore, provide the ability to set the idle state behaviour using a
new sysfs file, idle_state as a complement to the method of
instantiating the device via sysfs. The possible behaviours are
disconnect, i.e. to deselect all channels from the mux, as-is (the
default), i.e. leave the last channel selected, and set a
predetermined channel.
The current behaviour of leaving the channel as-is after each
transaction is preserved.
Signed-off-by: Robert Shearman <robert.shearman@xxxxxxx>
---
.../ABI/testing/sysfs-bus-i2c-devices-pca954x | 20 +++++
Should not ABI/... patches go to someone? Who? Did you use
get_maintainer.pl? I think you should at least include the main kernel
list? Maybe someone filters messages looking for ABI changes?
get_maintainer.pl doesn't recommend anything more than usual with the
presence of the ABI changes, but I can certainly copy LKML on the next
version of the series.
drivers/i2c/muxes/i2c-mux-pca954x.c | 84 +++++++++++++++++--
2 files changed, 97 insertions(+), 7 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x
diff --git a/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x b/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x
new file mode 100644
index 000000000000..809545a5f9e4
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x
@@ -0,0 +1,20 @@
+What: /sys/bus/i2c/.../idle_state
+Date: January 2019
+KernelVersion: 5.2
+Contact: Robert Shearman <robert.shearman@xxxxxxx>
+Description:
+ Value that can be written to control the behaviour of
+ the multiplexer on idle. Possible values:
+ -2 - disconnect on idle, i.e. deselect the last used
+ channel, which is useful when there is a device
+ with an address that conflicts with another
+ device on another pca954x mux on the same parent
Nit: It doesn't need to be a PCA954x mux, it could be any mux.
Ok, will fix. I'll remove the reference to mux here since it could be
any device and needn't be behind a mux.
Thanks,
Rob
