On Wed, 24 Apr 2024 18:20:41 +0300 Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > On Wed, Apr 24, 2024 at 3:59 PM Ondřej Jirman <megi@xxxxxx> wrote: > > On Wed, Apr 24, 2024 at 02:16:06AM GMT, Andy Shevchenko wrote: > > > On Wed, Apr 24, 2024 at 1:41 AM Aren Moynihan <aren@xxxxxxxxxxxxxxxxx> wrote: > > ... > > > > > ret = stk3310_init(indio_dev); > > > > if (ret < 0) > > > > - return ret; > > > > + goto err_vdd_disable; > > > > > > This is wrong. You will have the regulator being disabled _before_ > > > IRQ. Note, that the original code likely has a bug which sets states > > > before disabling IRQ and removing a handler. > > > > How so? stk3310_init is called before enabling the interrupt. > > Exactly, IRQ is registered with devm and hence the error path and > remove stages will got it in a wrong order. > > > Original code has a bug that IRQ is enabled before registering the > > IIO device, > > Indeed, but this is another bug. It shouldn't be. A device that produces interrupts before we have told it to is a) buggy, b) almost certainly already had it's interrupt masked due to spurious interrupt detection. Definitely don't want to do it in the opposite order where userspace could turn the device on and have it start generating interrupts before the irq is registered. I'd rather assume non buggy hardware (and that if there are bugs, the normal protections kick in) than introduce a race into the software. > > > so if IRQ is triggered before registration, iio_push_event > > from IRQ handler may be called on a not yet registered IIO device. > > > > Never saw it happen, though. :) > > Because nobody cares enough to enable DEBUG_SHIRQ In most devices there is a status register and we should be doing nothing unless that is set. Interestingly this device either doesn't have one or the driver doesn't read it - it reads a flag only and so will always push an event. Such a register read doesn't require the IIO device registration to be complete. There are corner cases where that isn't true that need to manually mask at the host but they are rare. There is also a basic level of defense in iio_push_event() against that being called when the event interface is not registered. Jonathan >
