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From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Linus Walleij <linus.walleij@linaro.org>,
	 Bartosz Golaszewski <brgl@bgdev.pl>
Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
	 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Subject: [PATCH 3/3] gpio: TODO: track the removal of GPIOD_FLAGS_BIT_NONEXCLUSIVE
Date: Mon, 31 Mar 2025 11:00:11 +0200	[thread overview]
Message-ID: <20250331-gpio-todo-remove-nonexclusive-v1-3-25f72675f304@linaro.org> (raw)
In-Reply-To: <20250331-gpio-todo-remove-nonexclusive-v1-0-25f72675f304@linaro.org>

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

This flag should be replaced by a better mechanism that counts the users
and properly manages the resources. The pwrseq subsystem is a good
candidate. GPIOs themselves should remain a unique resource. Add a task
for tracking the removal of GPIOD_FLAGS_BIT_NONEXCLUSIVE.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/TODO | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpio/TODO b/drivers/gpio/TODO
index b5f0a7a2e1bf1..5385071901993 100644
--- a/drivers/gpio/TODO
+++ b/drivers/gpio/TODO
@@ -186,3 +186,17 @@ their hardware offsets within the chip.
 
 Encourage users to switch to using them and eventually remove the existing
 global export/unexport attribues.
+
+-------------------------------------------------------------------------------
+
+Remove GPIOD_FLAGS_BIT_NONEXCLUSIVE
+
+This flag is an awful workaround that was created for some regulator
+corner-cases but got out of hand and is now used in at least 33 places
+treewide. Unlike what the intuition may tell users, it's not a reference
+counted mechanisms like what clocks or regulators use but just a raw access
+to the same GPIO descriptor from multiple places with no synchronization (other
+than what the underying driver offers). It doesn't even correctly support
+releasing the supposedly non-exclusive GPIOs. This whole thing should go and be
+replaced with a better solution - for exampe: using the relatively new power
+sequencing subsystem.

-- 
2.45.2


  parent reply	other threads:[~2025-03-31  9:00 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-31  9:00 [PATCH 0/3] gpio: deprecate and track the removal of the GPIOD_FLAGS_BIT_NONEXCLUSIVE flag Bartosz Golaszewski
2025-03-31  9:00 ` [PATCH 1/3] gpio: deprecate " Bartosz Golaszewski
2025-03-31  9:00 ` [PATCH 2/3] MAINTAINERS: add another keyword for the GPIO subsystem Bartosz Golaszewski
2025-03-31  9:00 ` Bartosz Golaszewski [this message]
2025-03-31 22:48   ` [PATCH 3/3] gpio: TODO: track the removal of GPIOD_FLAGS_BIT_NONEXCLUSIVE Linus Walleij
2025-04-01  8:57     ` Bartosz Golaszewski
2025-04-04  9:02       ` Linus Walleij
2025-04-07 12:38         ` Bartosz Golaszewski
2025-04-15  8:43           ` Linus Walleij
2025-04-17 18:45             ` Bartosz Golaszewski
2025-03-31 22:15 ` [PATCH 0/3] gpio: deprecate and track the removal of the GPIOD_FLAGS_BIT_NONEXCLUSIVE flag Linus Walleij

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