linux-kernel - [PATCH 1/6] gpio: TODO: remove the item about the new debugfs interface

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Message-Id: <20250321-gpio-todo-updates-v1-1-7b38f07110ee@linaro.org>
Date: Fri, 21 Mar 2025 16:49:33 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 1/6] gpio: TODO: remove the item about the new debugfs
 interface

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

The consensus among core GPIO stakeholders seems to be that a new
debugfs interface will only increase maintenance burden and will fail
to attract users that care about long-term stability of the ABI[1].
Let's not go this way and not add a fourth user-facing interface to the
GPIO subsystem.

[1] https://lore.kernel.org/all/9d3f1ca4-d865-45af-9032-c38cacc7fe93@pengutronix.de/

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/TODO | 36 ------------------------------------
 1 file changed, 36 deletions(-)

diff --git a/drivers/gpio/TODO b/drivers/gpio/TODO
index 942d1cd2bd3c9..9cf7b84cdb869 100644
--- a/drivers/gpio/TODO
+++ b/drivers/gpio/TODO
@@ -156,42 +156,6 @@ multiplexing, pin configuration, GPIO, etc selectable options in one
 and the same pin control and GPIO subsystem.
 
 
-Debugfs in place of sysfs
-
-The old sysfs code that enables simple uses of GPIOs from the
-command line is still popular despite the existance of the proper
-character device. The reason is that it is simple to use on
-root filesystems where you only have a minimal set of tools such
-as "cat", "echo" etc.
-
-The old sysfs still need to be strongly deprecated and removed
-as it relies on the global GPIO numberspace that assume a strict
-order of global GPIO numbers that do not change between boots
-and is independent of probe order.
-
-To solve this and provide an ABI that people can use for hacks
-and development, implement a debugfs interface to manipulate
-GPIO lines that can do everything that sysfs can do today: one
-directory per gpiochip and one file entry per line:
-
-/sys/kernel/debug/gpiochip/gpiochip0
-/sys/kernel/debug/gpiochip/gpiochip0/gpio0
-/sys/kernel/debug/gpiochip/gpiochip0/gpio1
-/sys/kernel/debug/gpiochip/gpiochip0/gpio2
-/sys/kernel/debug/gpiochip/gpiochip0/gpio3
-...
-/sys/kernel/debug/gpiochip/gpiochip1
-/sys/kernel/debug/gpiochip/gpiochip1/gpio0
-/sys/kernel/debug/gpiochip/gpiochip1/gpio1
-...
-
-The exact files and design of the debugfs interface can be
-discussed but the idea is to provide a low-level access point
-for debugging and hacking and to expose all lines without the
-need of any exporting. Also provide ample ammunition to shoot
-oneself in the foot, because this is debugfs after all.
-
-
 Moving over to immutable irq_chip structures
 
 Most of the gpio chips implementing interrupt support rely on gpiolib

-- 
2.45.2