[PATCH 3/3] iio: imu: adis: add a note better explaining state_lock

From: Alexandru Ardelean <alexandru.ardelean@analog.com>
To: <linux-iio@vger.kernel.org>
Cc: <jic23@kernel.org>, Alexandru Ardelean <alexandru.ardelean@analog.com>
Subject: [PATCH 3/3] iio: imu: adis: add a note better explaining state_lock
Date: Tue, 8 Oct 2019 11:02:39 +0300	[thread overview]
Message-ID: <20191008080239.23239-3-alexandru.ardelean@analog.com> (raw)
In-Reply-To: <20191008080239.23239-1-alexandru.ardelean@analog.com>

The `state_lock` mutex was renamed from `txrx_lock` in a previous patch and
is intended to be used by ADIS drivers to protect the state of devices
during consecutive R/W ops.
The initial patch that introduced this change did not do a good [well, any]
job at explaining this. This patch adds a comment to the `state_lock`
better explaining it's use.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 include/linux/iio/imu/adis.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/iio/imu/adis.h b/include/linux/iio/imu/adis.h
index 27ebd740f626..abd4bd07e960 100644
--- a/include/linux/iio/imu/adis.h
+++ b/include/linux/iio/imu/adis.h
@@ -80,6 +80,17 @@ struct adis {
 	const struct adis_data	*data;
 	struct adis_burst	*burst;
 
+	/**
+	 * The state_lock is meant to be used during operations that require
+	 * a sequence of SPI R/W in order to protect the SPI transfer
+	 * information (fields 'xfer', 'msg' & 'current_page') between
+	 * potential concurrent accesses.
+	 * This lock is used by all "adis_{functions}" that have to read/write
+	 * registers. These functions also have unlocked variants
+	 * (see "__adis_{functions}"), which don't hold this lock.
+	 * This allows users of the ADIS library to group SPI R/W into
+	 * the drivers, but they also must manage this lock themselves.
+	 */
 	struct mutex		state_lock;
 	struct spi_message	msg;
 	struct spi_transfer	*xfer;
-- 
2.20.1

