linux-kernel - [PATCH 19/19] soundwire: stream: make enable/disable/deprepare idempotent

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Date:   Wed, 26 Jan 2022 09:17:15 +0800
From:   Bard Liao <yung-chuan.liao@...ux.intel.com>
To:     alsa-devel@...a-project.org, vkoul@...nel.org
Cc:     vinod.koul@...aro.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, srinivas.kandagatla@...aro.org,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        bard.liao@...el.com
Subject: [PATCH 19/19] soundwire: stream: make enable/disable/deprepare idempotent

From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>

The stream management currently flags an 'inconsistent state' error
when a change is requested multiple times. This was added on purpose
to identify programming mistakes.

In hindsight, there was no real reason to fail if the logic at the
ASoC-DPCM level invokes the same callback multiple times. It's
perfectly acceptable to just return and not flag an error when there
is nothing to do. The main concern with the state management is to
trap errors such as trying to enable a stream that was not prepared
first.

This patch suggests allowing the stream functions to be idempotent,
i.e. they can be called multiple times.

Note that the prepare case was already handling multiple calls, this
was added in commit c32464c9393d ("soundwire: stream: only prepare
stream when it is configured.")

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Reviewed-by: Rander Wang <rander.wang@...el.com>
Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
---
 drivers/soundwire/stream.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index ccf3c99dd579..f273459b2023 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -1505,6 +1505,11 @@ int sdw_enable_stream(struct sdw_stream_runtime *stream)
 
 	sdw_acquire_bus_lock(stream);
 
+	if (stream->state == SDW_STREAM_ENABLED) {
+		ret = 0;
+		goto state_err;
+	}
+
 	if (stream->state != SDW_STREAM_PREPARED &&
 	    stream->state != SDW_STREAM_DISABLED) {
 		pr_err("%s: %s: inconsistent state state %d\n",
@@ -1588,6 +1593,11 @@ int sdw_disable_stream(struct sdw_stream_runtime *stream)
 
 	sdw_acquire_bus_lock(stream);
 
+	if (stream->state == SDW_STREAM_DISABLED) {
+		ret = 0;
+		goto state_err;
+	}
+
 	if (stream->state != SDW_STREAM_ENABLED) {
 		pr_err("%s: %s: inconsistent state state %d\n",
 		       __func__, stream->name, stream->state);
@@ -1663,6 +1673,11 @@ int sdw_deprepare_stream(struct sdw_stream_runtime *stream)
 
 	sdw_acquire_bus_lock(stream);
 
+	if (stream->state == SDW_STREAM_DEPREPARED) {
+		ret = 0;
+		goto state_err;
+	}
+
 	if (stream->state != SDW_STREAM_PREPARED &&
 	    stream->state != SDW_STREAM_DISABLED) {
 		pr_err("%s: %s: inconsistent state state %d\n",
-- 
2.17.1