[PATCH v3 01/14] pwm: Add an helper to prepare a new PWM state

Path	csiph.com!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Boris Brezillon <boris.brezillon@free-electrons.com>
Newsgroups	linux.kernel
Subject	[PATCH v3 01/14] pwm: Add an helper to prepare a new PWM state
Date	Tue, 14 Jun 2016 11:20:01 +0200
Message-ID	<rJSFP-2Rh-3@gated-at.bofh.it> (permalink)
References	<rJSFP-2Rh-5@gated-at.bofh.it>
X-Mailer	git-send-email 2.7.4
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	59
Organization	linux.* mail to news gateway
X-Original-Cc	Heiko Stuebner <heiko@sntech.de>, linux-rockchip@lists.infradead.org, Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>, Mark Rutland <mark.rutland@arm.com>, Ian Campbell <ijc+devicetree@hellion.org.uk>, Kumar Gala <galak@codeaurora.org>, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Milo Kim <milo.kim@ti.com>, Doug Anderson <dianders@google.com>, Caesar Wang <wxt@rock-chips.com>, Stephen Barber <smbarber@chromium.org>, Brian Norris <briannorris@chromium.org>, Ajit Pal Singh <ajitpal.singh@st.com>, Srinivas Kandagatla <srinivas.kandagatla@gmail.com>, Maxime Coquelin <maxime.coquelin@st.com>, Patrice Chotard <patrice.chotard@st.com>, kernel@stlinux.com, Laxman Dewangan <ldewangan@nvidia.com>, Boris Brezillon <boris.brezillon@free-electrons.com>
X-Original-Date	Tue, 14 Jun 2016 11:13:09 +0200
X-Original-Message-ID	<1465895602-31008-2-git-send-email-boris.brezillon@free-electrons.com>
X-Original-References	<1465895602-31008-1-git-send-email-boris.brezillon@free-electrons.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1421691

Show key headers only | View raw

The pwm_init_state() helper prepares a new state object containing the
current PWM state except for the polarity and period fields which are
set to the reference values (those in pwm_args).
This is particularly useful for PWM users who want to apply a new
duty-cycle expressed relatively to the reference period without
changing the enable state.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
---
 include/linux/pwm.h | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 17018f3..a100f6e 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -148,6 +148,39 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
 }
 
 /**
+ * pwm_init_state() - prepare a new state to be applied with pwm_apply_state()
+ * @pwm: PWM device
+ * @state: state to fill with the prepared PWM state
+ *
+ * This functions prepares a state that can later be tweaked and applied
+ * to the PWM device with pwm_apply_state(). This is a convenient function
+ * that first retrieves the current PWM state and the replaces the period
+ * and polarity fields with the reference values defined in pwm->args.
+ * Once the function returns, you can adjust the ->enabled and ->duty_cycle
+ * fields according to your needs before calling pwm_apply_state().
+ *
+ * ->duty_cycle is initially set to zero to avoid cases where the current
+ * ->duty_cycle value exceed the pwm_args->period one, which would trigger
+ * an error if the user calls pwm_apply_state() without adjusting ->duty_cycle
+ * first.
+ */
+static inline void pwm_init_state(const struct pwm_device *pwm,
+				  struct pwm_state *state)
+{
+	struct pwm_args args;
+
+	/* First get the current state. */
+	pwm_get_state(pwm, state);
+
+	/* Then fill it with the reference config */
+	pwm_get_args(pwm, &args);
+
+	state->period = args.period;
+	state->polarity = args.polarity;
+	state->duty_cycle = 0;
+}
+
+/**
  * struct pwm_ops - PWM controller operations
  * @request: optional hook for requesting a PWM
  * @free: optional hook for freeing a PWM
-- 
2.7.4

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH v3 01/14] pwm: Add an helper to prepare a new PWM state Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-06-14 11:20 +0200

csiph-web