Re: [PATCH] staging: iio: adc: ad7816: add timeout to busy-wait loop

[Andy Shevchenko]

On Thu, Feb 26, 2026 at 05:26:15AM +0000, Ruslan Valiyev wrote:
> The ad7816_spi_read() function polls the busy GPIO pin in a tight
> loop without any timeout. If the hardware fails to deassert the
> busy signal, the kernel hangs indefinitely in an unbounded
> busy-wait.
> 
> Replace the open-coded while/cpu_relax() loop with
> read_poll_timeout() which polls every 5 us and returns -ETIMEDOUT
> after 1 ms. Per the AD7816 datasheet the maximum conversion time
> is 27 us (temperature channel), so 1 ms provides generous margin.
> 
> Also handle the case where gpiod_get_value() returns a negative
> error code, which the original loop silently treated as not-busy.

...

> -		while (gpiod_get_value(chip->busy_pin))
> -			cpu_relax();
> +		int val;
> +
> +		ret = read_poll_timeout(gpiod_get_value, val, val <= 0,
> +					5, 1000, false, chip->busy_pin);
> +		if (val < 0)
> +			return val;
> +		if (ret)
> +			return ret;

Have you able to test this?

Have you investigated the code? It was an atomic, now it's sleeping.
This is a huge behavioural change. See my first Q.

-- 
With Best Regards,
Andy Shevchenko