bybrooklyn/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-04-18 06:44:00 -04:00
Code Issues Packages Projects Releases Wiki Activity

gpio: add gpio-line-mux driver

Browse Source 
Add a new driver which provides a 1-to-many mapping for a single real
GPIO using a multiplexer. Each virtual GPIO corresponds to a multiplexer
state which, if set for the multiplexer, connects the real GPIO to the
corresponding virtual GPIO.

This can help in various usecases. One practical case is the special
hardware design of the Realtek-based XS1930-10 switch from Zyxel. It
features two SFP+ ports/cages whose signals are wired directly to the
switch SoC. Although Realtek SoCs are short on GPIOs, there are usually
enough the fit the SFP signals without any hacks.

However, Zyxel did some weird design and connected RX_LOS, MOD_ABS and
TX_FAULT of one SFP cage onto a single GPIO line controlled by a
multiplexer (the same for the other SFP cage). The single multiplexer
controls the lines for both SFP and depending on the state, the
designated 'signal GPIO lines' are connected to one of the three SFP
signals.

Because the SFP core/driver doesn't support multiplexer but needs single
GPIOs for each of the signals, this driver fills the gap between both.
It registers a gpio_chip, provides multiple virtual GPIOs and sets the
backing multiplexer accordingly.

Due to several practical issues, this is input-only and doesn't support
IRQs.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Thomas Richard <thomas.richard@bootlin.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20251227180134.1262138-3-jelonek.jonas@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
This commit is contained in:
Jonas Jelonek
2025-12-27 18:01:34 +00:00
committed by Bartosz Golaszewski
parent 2a7618ba86
commit 2b03d9a40c
4 changed files with 142 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/gpio/Kconfig
View File

@@ -1994,6 +1994,15 @@ config GPIO_LATCH
Say yes here to enable a driver for GPIO multiplexers based on latches
connected to other GPIOs.
config GPIO_LINE_MUX
tristate "GPIO line mux driver"
depends on OF_GPIO
select MULTIPLEXER
help
Say Y here to support the GPIO line mux, which can provide virtual
GPIOs backed by a shared real GPIO and a multiplexer in a 1-to-many
fashion.
config GPIO_MOCKUP
tristate "GPIO Testing Driver (DEPRECATED)"
select IRQ_SIM