Linux Input/HID development
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From: "Alvin Šipraga" <alvin.sipraga@analog.com>
To: Michael Hennerich <michael.hennerich@analog.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Xiaolong Chen <xiaolong.chen@gmail.com>,
	Yuanbo Ye <yuan-bo.ye@motorola.com>, Tao Hu <taohu@motorola.com>
Cc: "Dmitry Torokhov" <dtor@mail.ru>, "Nuno Sá" <nuno.sa@analog.com>,
	linux-gpio@vger.kernel.org, linux-input@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Alvin Šipraga" <alvin.sipraga@analog.com>
Subject: [PATCH] Input: adp5588-keys - cache GPIO state before registering the gpiochip
Date: Tue, 18 Aug 2026 18:00:02 +0200	[thread overview]
Message-ID: <20260818-adp5588-gpio-cache-v1-1-650a2674fc0d@analog.com> (raw)

So as not to clobber any pre-programmed GPIO state in the execution
of its gpiochip ops, the driver caches things during probe time.
However, since those ops can be called both during and immediately after
the call to devm_gpiochip_add_data(), it is imperative that things are
cached before that. That's not the case right now, so reorder the two
steps to prevent any clobbering.

In a conrete example which motivated this change, a bootloader was
preconfiguring an important GPIO output to HIGH before booting the
kernel. Linux would then inadvertently set that output to LOW while
configuring a GPIO hog on a discrete GPIO line within the same 8-bit
bank (because the cached value was 0=LOW).

Fixes: ba9f507a1bea ("Input: adp5588-keys - export unused GPIO pins")
Signed-off-by: Alvin Šipraga <alvin.sipraga@analog.com>
---
 drivers/input/keyboard/adp5588-keys.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/input/keyboard/adp5588-keys.c b/drivers/input/keyboard/adp5588-keys.c
index 40371f5bd9ba..4f0ddff5baba 100644
--- a/drivers/input/keyboard/adp5588-keys.c
+++ b/drivers/input/keyboard/adp5588-keys.c
@@ -446,12 +446,6 @@ static int adp5588_gpio_add(struct adp5588_kpad *kpad)
 
 	mutex_init(&kpad->gpio_lock);
 
-	error = devm_gpiochip_add_data(dev, &kpad->gc, kpad);
-	if (error) {
-		dev_err(dev, "gpiochip_add failed: %d\n", error);
-		return error;
-	}
-
 	for (i = 0; i <= ADP5588_BANK(ADP5588_MAXGPIO); i++) {
 		kpad->dat_out[i] = adp5588_read(kpad->client,
 						GPIO_DAT_OUT1 + i);
@@ -459,6 +453,12 @@ static int adp5588_gpio_add(struct adp5588_kpad *kpad)
 		kpad->pull_dis[i] = adp5588_read(kpad->client, GPIO_PULL1 + i);
 	}
 
+	error = devm_gpiochip_add_data(dev, &kpad->gc, kpad);
+	if (error) {
+		dev_err(dev, "gpiochip_add failed: %d\n", error);
+		return error;
+	}
+
 	return 0;
 }
 

---
base-commit: 44f3468a0aef1aabdad551898ab7cfa2a9d20e99
change-id: 20260818-adp5588-gpio-cache-23fb8d0a3190

Best regards,
--  
Alvin Šipraga <alvin.sipraga@analog.com>


             reply	other threads:[~2026-08-18 16:00 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-18 16:00 Alvin Šipraga [this message]
2026-08-18 16:08 ` [PATCH] Input: adp5588-keys - cache GPIO state before registering the gpiochip Nuno Sá
2026-08-18 16:11 ` sashiko-bot
2026-08-18 16:27   ` Alvin Šipraga

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