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[23.88.128.2]) by smtp.gmail.com with ESMTPSA id 5614622812f47-47c43e6ae74sm49988b6e.3.2026.04.28.15.26.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 15:26:02 -0700 (PDT) From: Maxwell Doose To: songqiang1304521@gmail.com, jic23@kernel.org Cc: dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] iio: magnetometer: rm3100: Modernize locking and refactor control flow Date: Tue, 28 Apr 2026 17:26:00 -0500 Message-ID: <20260428222600.91322-1-m32285159@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace mutex_lock() and mutex_unlock() calls in rm3100-core.c with the more modern guard(mutex)() family. This will help modernize the driver and bring it up-to-date with modern available macros/functions. While replacing mutex_lock() and mutex_unlock(), the critical sections of rm3100_read_mag() and rm3100_get_samp_freq() have been extended to include negligible operations for cleaner logic. Add new helper-wrapper function rm3100_guarded_regmap_bulk_read() to help keep rm3100_trigger_handler() switch-cases clean while maintaining mutex locking and avoiding re-entrancy risks from potential callbacks. While at it, remove redundant gotos where applicable, and use direct returns instead. Suggested-by: Jonathan Cameron Signed-off-by: Maxwell Doose --- v2: - The following excerpts are from the original cover letter: - Added small style fixes per Andy's suggestions (Adding blank lines, moving an if statement in a scoped_guard block). - Switched out scoped_guard() for guard(mutex)() in certain commits. - Fixed error in commit 4 where deadlocks could occur, as goto ignores __attribute__((cleanup)). This has been fixed by the above. v3: - Added new helper-wrapper function rm3100_guarded_regmap_bulk_read(), see commit message. - Squashed commit into one commit rather than four. drivers/iio/magnetometer/rm3100-core.c | 94 ++++++++++++++------------ 1 file changed, 52 insertions(+), 42 deletions(-) diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c index 2b2884425746..9cad61e1df94 100644 --- a/drivers/iio/magnetometer/rm3100-core.c +++ b/drivers/iio/magnetometer/rm3100-core.c @@ -204,27 +204,23 @@ static int rm3100_read_mag(struct rm3100_data *data, int idx, int *val) u8 buffer[3]; int ret; - mutex_lock(&data->lock); + guard(mutex)(&data->lock); + ret = regmap_write(regmap, RM3100_REG_POLL, BIT(4 + idx)); if (ret < 0) - goto unlock_return; + return ret; ret = rm3100_wait_measurement(data); if (ret < 0) - goto unlock_return; + return ret; ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * idx, buffer, 3); if (ret < 0) - goto unlock_return; - mutex_unlock(&data->lock); + return ret; *val = sign_extend32(get_unaligned_be24(&buffer[0]), 23); return IIO_VAL_INT; - -unlock_return: - mutex_unlock(&data->lock); - return ret; } #define RM3100_CHANNEL(axis, idx) \ @@ -284,11 +280,12 @@ static int rm3100_get_samp_freq(struct rm3100_data *data, int *val, int *val2) unsigned int tmp; int ret; - mutex_lock(&data->lock); + guard(mutex)(&data->lock); + ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp); - mutex_unlock(&data->lock); if (ret < 0) return ret; + *val = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][0]; *val2 = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][1]; @@ -338,56 +335,50 @@ static int rm3100_set_samp_freq(struct iio_dev *indio_dev, int val, int val2) int ret; int i; - mutex_lock(&data->lock); + guard(mutex)(&data->lock); + /* All cycle count registers use the same value. */ ret = regmap_read(regmap, RM3100_REG_CC_X, &cycle_count); if (ret < 0) - goto unlock_return; + return ret; for (i = 0; i < RM3100_SAMP_NUM; i++) { if (val == rm3100_samp_rates[i][0] && val2 == rm3100_samp_rates[i][1]) break; } - if (i == RM3100_SAMP_NUM) { - ret = -EINVAL; - goto unlock_return; - } + if (i == RM3100_SAMP_NUM) + return -EINVAL; ret = regmap_write(regmap, RM3100_REG_TMRC, i + RM3100_TMRC_OFFSET); if (ret < 0) - goto unlock_return; + return ret; /* Checking if cycle count registers need changing. */ if (val == 600 && cycle_count == 200) { ret = rm3100_set_cycle_count(data, 100); if (ret < 0) - goto unlock_return; + return ret; } else if (val != 600 && cycle_count == 100) { ret = rm3100_set_cycle_count(data, 200); if (ret < 0) - goto unlock_return; + return ret; } if (iio_buffer_enabled(indio_dev)) { /* Writing TMRC registers requires CMM reset. */ ret = regmap_write(regmap, RM3100_REG_CMM, 0); if (ret < 0) - goto unlock_return; + return ret; ret = regmap_write(data->regmap, RM3100_REG_CMM, (*indio_dev->active_scan_mask & 0x7) << RM3100_CMM_AXIS_SHIFT | RM3100_CMM_START); if (ret < 0) - goto unlock_return; + return ret; } - mutex_unlock(&data->lock); data->conversion_time = rm3100_samp_rates[i][2] * 2; return 0; - -unlock_return: - mutex_unlock(&data->lock); - return ret; } static int rm3100_read_raw(struct iio_dev *indio_dev, @@ -458,6 +449,28 @@ static const struct iio_buffer_setup_ops rm3100_buffer_ops = { .postdisable = rm3100_buffer_postdisable, }; +/** + * rm3100_guarded_regmap_bulk_read() - Wrapper around regmap_bulk_read() with a mutex + * + * @lock: Mutex to lock while performing operations + * @map: Register map to read from, passed to regmap_bulk_read() + * @reg: First register to be read from, passed to regmap_bulk_read() + * @val: Pointer to store read value, in native register size for device, + * passed to regmap_bulk_read() + * @val_count: Number of registers to read, passed to regmap_bulk_read() + * + * Intended for use only in rm3100_trigger_handler(). + * + * A value of zero will be returned on success, a negative errno will + * be returned in error cases. + */ +static int rm3100_guarded_regmap_bulk_read(struct mutex *lock, struct regmap *map, + unsigned int reg, void *val, size_t val_count) +{ + guard(mutex)(lock); + return regmap_bulk_read(map, reg, val, val_count); +} + static irqreturn_t rm3100_trigger_handler(int irq, void *p) { struct iio_poll_func *pf = p; @@ -468,11 +481,10 @@ static irqreturn_t rm3100_trigger_handler(int irq, void *p) struct regmap *regmap = data->regmap; int ret, i, bit; - mutex_lock(&data->lock); switch (scan_mask) { case BIT(0) | BIT(1) | BIT(2): - ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9); - mutex_unlock(&data->lock); + ret = rm3100_guarded_regmap_bulk_read(&data->lock, regmap, RM3100_REG_MX2, + data->buffer, 9); if (ret < 0) goto done; /* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for paddings. */ @@ -480,36 +492,34 @@ static irqreturn_t rm3100_trigger_handler(int irq, void *p) memmove(data->buffer + i * 4, data->buffer + i * 3, 3); break; case BIT(0) | BIT(1): - ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 6); - mutex_unlock(&data->lock); + ret = rm3100_guarded_regmap_bulk_read(&data->lock, regmap, RM3100_REG_MX2, + data->buffer, 6); if (ret < 0) goto done; memmove(data->buffer + 4, data->buffer + 3, 3); break; case BIT(1) | BIT(2): - ret = regmap_bulk_read(regmap, RM3100_REG_MY2, data->buffer, 6); - mutex_unlock(&data->lock); + ret = rm3100_guarded_regmap_bulk_read(&data->lock, regmap, RM3100_REG_MY2, + data->buffer, 6); if (ret < 0) goto done; memmove(data->buffer + 4, data->buffer + 3, 3); break; case BIT(0) | BIT(2): - ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9); - mutex_unlock(&data->lock); + ret = rm3100_guarded_regmap_bulk_read(&data->lock, regmap, RM3100_REG_MX2, + data->buffer, 9); if (ret < 0) goto done; memmove(data->buffer + 4, data->buffer + 6, 3); break; default: for_each_set_bit(bit, &scan_mask, mask_len) { - ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * bit, - data->buffer, 3); - if (ret < 0) { - mutex_unlock(&data->lock); + ret = rm3100_guarded_regmap_bulk_read(&data->lock, regmap, + RM3100_REG_MX2 + 3 * bit, + data->buffer, 3); + if (ret < 0) goto done; - } } - mutex_unlock(&data->lock); } /* * Always using the same buffer so that we wouldn't need to set the -- 2.53.0