From d795e38df4b7ebac1072bbf7d8a5500c1ea83332 Mon Sep 17 00:00:00 2001 From: Jonathan Cameron Date: Sun, 9 Feb 2025 18:05:58 +0000 Subject: iio: core: Rework claim and release of direct mode to work with sparse. Initial thought was to do something similar to __cond_lock() do_iio_device_claim_direct_mode(iio_dev) ? : ({ __acquire(iio_dev); 0; }) + Appropriate static inline iio_device_release_direct_mode() However with that, sparse generates false positives. E.g. drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c:1811:17: warning: context imbalance in 'st_lsm6dsx_read_raw' - unexpected unlock So instead, this patch rethinks the return type and makes it more 'conditional lock like' (which is part of what is going on under the hood anyway) and return a boolean - true for successfully acquired, false for did not acquire. To allow a migration path given the rework is now non trivial, take a leaf out of the naming of the conditional guard we currently have for IIO device direct mode and drop the _mode postfix from the new functions giving iio_device_claim_direct() and iio_device_release_direct() Whilst the kernel supports __cond_acquires() upstream sparse does not yet do so. Hence rely on sparse expanding a static inline wrapper to explicitly see whether __acquire() is called. Note that even with the solution here, sparse sometimes gives false positives. However in the few cases seen they were complex code structures that benefited from simplification anyway. Reviewed-by: David Lechner Reviewed-by: Nuno Sa Link: https://patch.msgid.link/20250209180624.701140-2-jic23@kernel.org Signed-off-by: Jonathan Cameron --- include/linux/iio/iio.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'include') diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h index 56161e02f002..5ed03e36178f 100644 --- a/include/linux/iio/iio.h +++ b/include/linux/iio/iio.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #include /* IIO TODO LIST */ @@ -662,6 +663,31 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp); int iio_device_claim_direct_mode(struct iio_dev *indio_dev); void iio_device_release_direct_mode(struct iio_dev *indio_dev); +/* + * Helper functions that allow claim and release of direct mode + * in a fashion that doesn't generate many false positives from sparse. + * Note this must remain static inline in the header so that sparse + * can see the __acquire() marking. Revisit when sparse supports + * __cond_acquires() + */ +static inline bool iio_device_claim_direct(struct iio_dev *indio_dev) +{ + int ret = iio_device_claim_direct_mode(indio_dev); + + if (ret) + return false; + + __acquire(iio_dev); + + return true; +} + +static inline void iio_device_release_direct(struct iio_dev *indio_dev) +{ + iio_device_release_direct_mode(indio_dev); + __release(indio_dev); +} + /* * This autocleanup logic is normally used via * iio_device_claim_direct_scoped(). -- cgit v1.2.3