Re: [PATCH 5.10 073/593] iio: light: tcs3472: do not free unallocated IRQ

On Tue, 13 Jul 2021 23:31:28 +0200
Pavel Machek [off-list ref] wrote:

Hi!

quoted

commit 7cd04c863f9e1655d607705455e7714f24451984 upstream.

Allocating an IRQ is conditional to the IRQ existence, but freeing it
was not. If no IRQ was allocate, the driver would still try to free
IRQ 0. Add the missing checks.

This fixes the following trace when the driver is removed:

[  100.667788] Trying to free already-free IRQ 0  

AFAICT this will need more fixing, because IRQ == 0 is a valid
IRQ. NO_IRQ (aka -1) should be safe to use for "no irq assigned".

I thought we had long put this to bed.  IRQ == 0 is not a valid irq number.
If there is an error in parsing DT (e.g. no irq specified) it returns 0
not NO_IRQ.  Naturally irq chips can have a 0, but that's pre translation to
virtual IRQ space.

Many years ago, ARM did have 0 as as valid IRQ, but that got cleaned up
to make it easier to do generic code like this.

Jonathan

Best regards,
								Pavel

quoted

+++ b/drivers/iio/light/tcs3472.c

@@ -531,7 +531,8 @@ static int tcs3472_probe(struct i2c_clie
 	return 0;
 
 free_irq:
-	free_irq(client->irq, indio_dev);
+	if (client->irq)
+		free_irq(client->irq, indio_dev);
 buffer_cleanup:
 	iio_triggered_buffer_cleanup(indio_dev);
 	return ret;