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-rw-r--r--Documentation/pwm.txt27
1 files changed, 23 insertions, 4 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 48f598acdd16..554290ebab94 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -12,14 +12,33 @@ this kind of flexibility the generic PWM API exists.
Identifying PWMs
----------------
-Users of the legacy PWM API use unique IDs to refer to PWM devices. One
-goal of the new PWM framework is to get rid of this global namespace.
+Users of the legacy PWM API use unique IDs to refer to PWM devices.
+
+Instead of referring to a PWM device via its unique ID, board setup code
+should instead register a static mapping that can be used to match PWM
+consumers to providers, as given in the following example:
+
+ static struct pwm_lookup board_pwm_lookup[] = {
+ PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL),
+ };
+
+ static void __init board_init(void)
+ {
+ ...
+ pwm_add_table(board_pwm_lookup, ARRAY_SIZE(board_pwm_lookup));
+ ...
+ }
Using PWMs
----------
-A PWM can be requested using pwm_request() and freed after usage with
-pwm_free(). After being requested a PWM has to be configured using
+Legacy users can request a PWM device using pwm_request() and free it
+after usage with pwm_free().
+
+New users should use the pwm_get() function and pass to it the consumer
+device or a consumer name. pwm_put() is used to free the PWM device.
+
+After being requested a PWM has to be configured using:
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);