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

[Klara Modin <klarasmodin@gmail.com>]

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On 2024-10-24 13:45, Bartosz Golaszewski wrote:
> On Thu, 24 Oct 2024 13:34:11 +0200, Klara Modin <klarasmodin@gmail.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

That doesn't seem to change anything significantly:

Call Trace:
gpiod_direction_output (drivers/gpio/gpiolib.c:4165 
drivers/gpio/gpiolib.c:2701 drivers/gpio/gpiolib.c:2695)
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)

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