linux-kernel - Re: [PATCH v5 8/8] gpiolib: notify user-space about in-kernel line state changes

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Message-ID: <CAMRc=McUpRJ=EN3DB7gsgsNKZHhJym6vfURmX9+mXnYuXjNwMA@mail.gmail.com>
Date: Thu, 24 Oct 2024 04:45:18 -0700
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Klara Modin <klarasmodin@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Kent Gibson <warthog618@...il.com>, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v5 8/8] gpiolib: notify user-space about in-kernel line
 state changes

On Thu, 24 Oct 2024 13:34:11 +0200, Klara Modin <klarasmodin@...il.com> said:
>
> I think I hit the same, or a similar bug, on my Edgerouter 6P (Cavium
> Octeon III):
>
> CPU 3 Unable to handle kernel paging request at virtual address
> 0000000000000000, epc == ffffffff817a40c8, ra == ffffffff817a40a4
> Oops[#1]:
> CPU: 3 UID: 0 PID: 1 Comm: swapper/0 Not tainted
> 6.12.0-rc4-next-20241023-00032-g01c8e35f8d89 #84
> ...
> Call Trace:
> gpiod_direction_output (drivers/gpio/gpiolib.c:4164
> drivers/gpio/gpiolib.c:2700 drivers/gpio/gpiolib.c:2694)
> i2c_register_adapter (drivers/i2c/i2c-core-base.c:396
> drivers/i2c/i2c-core-base.c:422 drivers/i2c/i2c-core-base.c:434
> drivers/i2c/i2c-core-base.c:1574)
> octeon_i2c_probe (drivers/i2c/busses/i2c-octeon-platdrv.c:247)
>
> (the complete log is attached)
>
> Unfortunately the oops remains after applying the diff and the call
> trace looks to be the same.
>
> Please let me know if there's anything else you need.
>

Hmm so it's desc->gdev that is NULL... Could you try the following:

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ae758ba6dc3d..c95c79ea2b49 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1026,6 +1026,9 @@ int gpiochip_add_data_with_key(struct gpio_chip
*gc, void *data,
 		}
 	}

+	for (desc_index = 0; desc_index < gc->ngpio; desc_index++)
+		gdev->descs[desc_index].gdev = gdev;
+
 	ATOMIC_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
 	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);

@@ -1055,8 +1058,6 @@ int gpiochip_add_data_with_key(struct gpio_chip
*gc, void *data,
 	for (desc_index = 0; desc_index < gc->ngpio; desc_index++) {
 		struct gpio_desc *desc = &gdev->descs[desc_index];

-		desc->gdev = gdev;
-
 		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) {
 			assign_bit(FLAG_IS_OUT,
 				   &desc->flags, !gc->get_direction(gc, desc_index));

I'm wondering if this is not an earlier commit.

Bart