From: Ruslan Valiyev <linuxoid@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
Lars-Peter Clausen <lars@metafoo.de>,
Michael Hennerich <Michael.Hennerich@analog.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
David Lechner <dlechner@baylibre.com>,
Nuno Sa <nuno.sa@analog.com>,
linux-iio@vger.kernel.org, linux-staging@lists.linux.dev,
linux-kernel@vger.kernel.org, Ruslan Valiyev <linuxoid@gmail.com>
Subject: Re: [PATCH] staging: iio: adc: ad7816: add timeout to busy-wait loop
Date: Thu, 26 Feb 2026 08:25:35 +0000 [thread overview]
Message-ID: <20260226082535.69503-1-linuxoid@gmail.com> (raw)
In-Reply-To: <aZ_9x4q5BZRJi3ue@smile.fi.intel.com>
On Thu, Feb 26, 2026 at 05:26:15AM +0000, Andy Shevchenko wrote:
> Have you able to test this?
No, I don't have AD7816 hardware, compile-tested only.
> Have you investigated the code? It was an atomic, now it's sleeping.
> This is a huge behavioural change. See my first Q.
You're right, the sleeping change was unnecessary. ad7816_spi_read()
is only called from ad7816_show_value(), a sysfs show callback, so
it runs in process context. But for a wait of at most 27 us per the
datasheet, there's no benefit to sleeping. The atomic variant adds
the timeout protection while preserving the original busy-wait
semantics.
I've respun as v2 using read_poll_timeout_atomic(). Also fixed the
commit message: v1 incorrectly said the original loop treated
negative gpiod_get_value() errors as "not-busy", it's the opposite,
negative is non-zero so the loop treats it as busy and spins forever.
Ruslan
next prev parent reply other threads:[~2026-02-26 8:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-26 5:26 [PATCH] staging: iio: adc: ad7816: add timeout to busy-wait loop Ruslan Valiyev
2026-02-26 8:01 ` Andy Shevchenko
2026-02-26 8:25 ` Ruslan Valiyev [this message]
2026-02-26 9:20 ` Dan Carpenter
2026-02-26 8:25 ` [PATCH v2] " Ruslan Valiyev
2026-02-26 9:15 ` Andy Shevchenko
2026-02-26 9:29 ` Ruslan Valiyev
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