Re: [PATCH v2] iio: accel: bmc150: Fix irq assumption regression

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Mon, Nov 03, 2025 at 10:36:18AM +0100, Linus Walleij wrote:
> 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)

These 3 lines are not important.


> 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

As Submitting Patches recommends the commit message is better when it has less
(unrelated) lines in traceback(s). I already mentioned that those 4 lines and
more are not needed (important), and maybe removed. I leave it to Jonathan to
tweak whilst applying.

> This bug seems to have been in the driver since the beginning,
> but it only manifests recently, I do not know why.
> 
> Store the IRQ number in the state struct, as this is a common
> pattern in other drivers, then use this to determine if we have
> IRQ support or not.

I would just assign the returned value of irq to the data field and hence drop
the '=' in ' <= 0', but I am not going to pursue this. Up to you.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

-- 
With Best Regards,
Andy Shevchenko