[PATCH 1/2] PWM: add pwm framework support

On Tue, Jun 28, 2011 at 02:27:04PM +0200, Arnd Bergmann wrote:

On Tuesday 28 June 2011, Sascha Hauer wrote:

quoted

This patch adds framework support for PWM (pulse width modulation) devices.

The is a barebone PWM API already in the kernel under include/linux/pwm.h,
but it does not allow for multiple drivers as each of them implements the
pwm_*() functions.

Hi Sascha,

This looks very nice.
I have only trivial comments, except for the suggestion to use idr.
 

quoted

+PWM core
+M:	Sascha Hauer [off-list ref]
+L:	linux-kernel at vger.kernel.org
+S:	Maintained

I would add

F:	drivers/pwm/

quoted

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
new file mode 100644
index 0000000..93c1052
--- /dev/null
+++ b/drivers/pwm/Kconfig

@@ -0,0 +1,12 @@
+menuconfig PWM
+	bool "PWM Support"
+	help
+	  This enables PWM support through the generic PWM framework.
+	  You only need to enable this, if you also want to enable
+	  one or more of the PWM drivers below.

Remove the comma.

quoted

+
+/*
+ * The next pwm id to assign. We do not bother to fill gaps which
+ * occur during dynamic registering/deregistering of pwms, but
+ * instead assign a uniq id to each new pwm.

                       unique

quoted

+ */
+static int next_pwm_id;

How about using idr? It provides you a fast lookup and handles giving
out unique numbers.

Sounds like a good idea, but is idr compatible with the pwmchip_reserve
function below? idr gives no guarantee that the first id is zero, but I
need exactly this to make the ids for the internal PWMs known at compile
time.

(In the longer term it probably makes sense to implement a
pwm_get(struct device *, const char *id) similar to the clk api, I just
wanted to stay compatible to the current PWM API for now)

Sascha


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