linux-kernel - [PATCH v2 1/7] iio: core: add read_avail_release

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Message-Id: <20241007-iio-read-avail-release-v2-1-245002d5869e@gmail.com>
Date: Mon, 07 Oct 2024 10:37:10 +0200
From: Matteo Martelli <matteomartelli3@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Alisa-Dariana Roman <alisa.roman@...log.com>, 
 Christian Eggers <ceggers@...i.de>, Peter Rosin <peda@...ntia.se>, 
 Paul Cercueil <paul@...pouillou.net>, Sebastian Reichel <sre@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-mips@...r.kernel.org, linux-pm@...r.kernel.org, 
 Matteo Martelli <matteomartelli3@...il.com>
Subject: [PATCH v2 1/7] iio: core: add read_avail_release_resource callback
 to fix race

Some iio drivers currently share an available info buffer that might be
changed while iio core prints it to sysfs. To avoid the buffer
corruption, add a release callback to let iio drivers allocate a copy of
the available info buffer and later free it in the release callback.
Such control is kept in the driver logic so that some driver that needs
a big available info buffer might also perform some check to keep the
copied buffer around in case no race has occurred.

Signed-off-by: Matteo Martelli <matteomartelli3@...il.com>
---
 drivers/iio/industrialio-core.c | 14 +++++++++++---
 include/linux/iio/iio.h         |  4 ++++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 6a6568d4a2cb3a3f63381d5a6f25a2881b3ba2ed..4aea9de9f15a4d70f9d02fb3d47df49eef8c8423 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -859,12 +859,20 @@ static ssize_t iio_read_channel_info_avail(struct device *dev,
 		return ret;
 	switch (ret) {
 	case IIO_AVAIL_LIST:
-		return iio_format_avail_list(buf, vals, type, length);
+		ret = iio_format_avail_list(buf, vals, type, length);
+		break;
 	case IIO_AVAIL_RANGE:
-		return iio_format_avail_range(buf, vals, type);
+		ret = iio_format_avail_range(buf, vals, type);
+		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
 	}
+
+	if (indio_dev->info->read_avail_release_resource)
+		indio_dev->info->read_avail_release_resource(
+			indio_dev, this_attr->c, vals, this_attr->address);
+
+	return ret;
 }
 
 /**
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 18779b631e9071801958fc9d50b941b548fab940..55326f0310b2e9b3fa561c4728e7eabe1d7a5e78 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -491,6 +491,10 @@ struct iio_info {
 			  int *length,
 			  long mask);
 
+	void (*read_avail_release_resource)(struct iio_dev *indio_dev,
+					    struct iio_chan_spec const *chan,
+					    const int *vals, long mask);
+
 	int (*write_raw)(struct iio_dev *indio_dev,
 			 struct iio_chan_spec const *chan,
 			 int val,

-- 
2.46.2