ASoC: omap-abe-twl6040: Add device tree support

[deliverable/linux.git] / Documentation / pwm.txt

diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 03e39d145911401f110200b7f5587d38c8470584..554290ebab94509f6fa9ae603cadfc3b8afcde4a 100644 (file)
--- 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);
 
@@ -33,9 +52,12 @@ there only has been the barebone API meaning that each driver has
 to implement the pwm_*() functions itself. This means that it's impossible
 to have multiple PWM drivers in the system. For this reason it's mandatory
 for new drivers to use the generic PWM framework.
-A new PWM device can be added using pwmchip_add() and removed again with
-pwmchip_remove(). pwmchip_add() takes a filled in struct pwm_chip as
-argument which provides the ops and the pwm id to the framework.
+
+A new PWM controller/chip can be added using pwmchip_add() and removed
+again with pwmchip_remove(). pwmchip_add() takes a filled in struct
+pwm_chip as argument which provides a description of the PWM chip, the
+number of PWM devices provider by the chip and the chip-specific
+implementation of the supported PWM operations to the framework.
 
 Locking
 -------