We recently introduced a bug when we tried to convert of_iomap() to devm_of_iomap(). The problem was that there were two drivers mapping the same io region. The first driver was using of_iomap() and the second driver was using devm_of_iomap() and the kernel booted fine. When we converted the first drive to use devm_of_iomap() then the second driver failed with -EBUSY and the kernel couldn't boot. Let's add a comment to prevent this sort of mistake in the future. Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> --- lib/devres.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/devres.c b/lib/devres.c index 6ef51f159c54b..0abe7c1cc4681 100644 --- a/lib/devres.c +++ b/lib/devres.c @@ -204,6 +204,12 @@ void __iomem *devm_ioremap_resource_wc(struct device *dev, * base = devm_of_iomap(&pdev->dev, node, 0, NULL); * if (IS_ERR(base)) * return PTR_ERR(base); + * + * Please Note: This is not a one-to-one replacement for of_iomap() because the + * of_iomap() function does not track whether the region is already mapped. If + * two drivers try to map the same memory, the of_iomap() function will succeed + * but the the devm_of_iomap() function will return -EBUSY. + * */ void __iomem *devm_of_iomap(struct device *dev, struct device_node *node, int index, resource_size_t *size) -- 2.26.2
