[PATCH] irq: Check if someone is overwriting the irq chip data

[Holger Hans Peter Freyther]

This tries to establish the semantic that one can either
set the chip data to NULL or if it is NULL to some value
but never overwrite a non NULL value.

Signed-off-by: Holger Hans Peter Freyther <zecke at selfish.org>
---
 kernel/irq/chip.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index d5a3009..25e446d 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -123,6 +123,10 @@ int irq_set_chip_data(unsigned int irq, void *data)

 	if (!desc)
 		return -EINVAL;
+
+	BUG_ON(data && desc->irq_data.chip_data &&
+		data != desc->irq_data.chip_data);
+
 	desc->irq_data.chip_data = data;
 	irq_put_desc_unlock(desc, flags);
 	return 0;
-- 
1.7.4.1