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authorDan Carpenter <dan.carpenter@oracle.com>2020-06-09 13:46:42 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-07-10 14:15:55 +0200
commit7ae731a8441d70e5fb6144422a675bf1b2d6ace9 (patch)
treee6ab0a16c839a4caa2a3387ee469e4704b66a333 /lib/devres.c
parent35bd8c07db2ce8fd2834ef866240613a4ef982e7 (diff)
lib: devres: add a comment about the devm_of_iomap() function
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@oracle.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20200609104642.GA43074@mwanda Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/devres.c')
-rw-r--r--lib/devres.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/lib/devres.c b/lib/devres.c
index ca0d28727cce..ebb1573d9ae3 100644
--- a/lib/devres.c
+++ b/lib/devres.c
@@ -213,6 +213,12 @@ 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)