[PATCH] iio: accel: bmc150: Fix irq assumption regression

[Linus Walleij <linus.walleij@linaro.org>]

The code in bmc150-accel-core.c unconditionally calls
bmc150_accel_set_interrupt() in the iio_buffer_setup_ops,
such as on the runtime PM resume path giving a kernel
splat like this if the device has no interrupts:

Unable to handle kernel NULL pointer dereference at virtual
  address 00000001 when read
CPU: 0 UID: 0 PID: 393 Comm: iio-sensor-prox Not tainted
  6.18.0-rc1-postmarketos-stericsson-00001-g6b43386e3737 #73 PREEMPT
Hardware name: ST-Ericsson Ux5x0 platform (Device Tree Support)
PC is at bmc150_accel_set_interrupt+0x98/0x194
LR is at __pm_runtime_resume+0x5c/0x64
(...)
Call trace:
bmc150_accel_set_interrupt from bmc150_accel_buffer_postenable+0x40/0x108
bmc150_accel_buffer_postenable from __iio_update_buffers+0xbe0/0xcbc
__iio_update_buffers from enable_store+0x84/0xc8
enable_store from kernfs_fop_write_iter+0x154/0x1b4
kernfs_fop_write_iter from do_iter_readv_writev+0x178/0x1e4
do_iter_readv_writev from vfs_writev+0x158/0x3f4
vfs_writev from do_writev+0x74/0xe4
do_writev from __sys_trace_return+0x0/0x10

This bug seems to have been in the driver since the beginning,
but it only manifests recently, I do not know why.

Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/iio/accel/bmc150-accel-core.c | 5 +++++
 drivers/iio/accel/bmc150-accel.h      | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index 3c5d1560b163..f4421a3b0ef2 100644
--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -523,6 +523,10 @@ static int bmc150_accel_set_interrupt(struct bmc150_accel_data *data, int i,
 	const struct bmc150_accel_interrupt_info *info = intr->info;
 	int ret;
 
+	/* We do not always have an IRQ */
+	if (!data->has_irq)
+		return 0;
+
 	if (state) {
 		if (atomic_inc_return(&intr->users) > 1)
 			return 0;
@@ -1696,6 +1700,7 @@ int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
 	}
 
 	if (irq > 0) {
+		data->has_irq = true;
 		ret = devm_request_threaded_irq(dev, irq,
 						bmc150_accel_irq_handler,
 						bmc150_accel_irq_thread_handler,
diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
index 7a7baf52e595..6e9bb69a1fd4 100644
--- a/drivers/iio/accel/bmc150-accel.h
+++ b/drivers/iio/accel/bmc150-accel.h
@@ -59,6 +59,7 @@ enum bmc150_accel_trigger_id {
 struct bmc150_accel_data {
 	struct regmap *regmap;
 	struct regulator_bulk_data regulators[2];
+	bool has_irq;
 	struct bmc150_accel_interrupt interrupts[BMC150_ACCEL_INTERRUPTS];
 	struct bmc150_accel_trigger triggers[BMC150_ACCEL_TRIGGERS];
 	struct mutex mutex;

---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251027-fix-bmc150-7e568122b265

Best regards,
-- 
Linus Walleij <linus.walleij@linaro.org>