Re: [PATCH 7/7] arch/unicore32/kernel/dma.c: ensure arguments to request_irq and free_irq are compatible

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On Tue, 13 Mar 2012, Guan Xuetao wrote:

On Mon, 2012-03-12 at 06:27 +0100, Julia Lawall wrote:
On Mon, 12 Mar 2012, Guan Xuetao wrote:

On Sun, 2012-03-11 at 20:36 +0100, Julia Lawall wrote:
From: Julia Lawall <Julia.Lawall@xxxxxxx>

Convert calls to free_irq so that the second argument is the same as the
last argument of the corresponding call to request_irq, rather than the
second to last.  Without this property, free_irq does nothing.

Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxx>

---
 arch/unicore32/kernel/dma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/unicore32/kernel/dma.c b/arch/unicore32/kernel/dma.c
index ae441bc..c813fec 100644
--- a/arch/unicore32/kernel/dma.c
+++ b/arch/unicore32/kernel/dma.c
@@ -173,7 +173,7 @@ int __init puv3_init_dma(void)
 	ret = request_irq(IRQ_DMAERR, dma_err_handler, 0, "DMAERR", NULL);
 	if (ret) {
 		printk(KERN_CRIT "Can't register IRQ for DMAERR\n");
-		free_irq(IRQ_DMA, "DMA");
+		free_irq(IRQ_DMA, NULL);
 		return ret;
 	}

Yeah, it's an obvious mistake. Thanks.
Because the dma device is just located inside PKUnity-3 SoC, and
request_irq() should always return 0, I prefer to remove this free_irq()
line.

Remove the whole if test I guess.  Is there a nce way to indicate that the
return value is not needed (eg for the benefit of future bug finding
rules)?

julia
In this case, removing the line containing free_irq() is well enough,
because IRQ_DMA can work even when IRQ_DMAERR doesn't work. And we need
printk and error return value to get potential logical bug information.

I'm not completely sure to understand. The point is that the first request_irq can never fail, so we don't need to clean up when the second one fails? Because the lack of cleaning up will not cause the first one to fail the next time? free_irq removes an action from a list and does a module_put. Are these operations both not needed?

thanks,julia
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