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-rw-r--r--Documentation/gpio.txt5
1 files changed, 3 insertions, 2 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 18022e249c53..8a7c45956d24 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -264,7 +264,7 @@ map between them using calls like:
/* map GPIO numbers to IRQ numbers */
int gpio_to_irq(unsigned gpio);
- /* map IRQ numbers to GPIO numbers */
+ /* map IRQ numbers to GPIO numbers (avoid using this) */
int irq_to_gpio(unsigned irq);
Those return either the corresponding number in the other namespace, or
@@ -284,7 +284,8 @@ system wakeup capabilities.
Non-error values returned from irq_to_gpio() would most commonly be used
with gpio_get_value(), for example to initialize or update driver state
-when the IRQ is edge-triggered.
+when the IRQ is edge-triggered. Note that some platforms don't support
+this reverse mapping, so you should avoid using it.
Emulating Open Drain Signals