linux-kernel - [PATCH v7 2/4] firmware: drop bit ops in favor of simple state machine

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Date:   Thu, 17 Nov 2016 11:00:49 +0100
From:   Daniel Wagner <wagi@...om.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ming Lei <ming.lei@...onical.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Takashi Iwai <tiwai@...e.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arend van Spriel <arend.vanspriel@...adcom.com>,
        Yves-Alexis Perez <corsac@...sac.net>,
        Daniel Wagner <daniel.wagner@...-carit.de>
Subject: [PATCH v7 2/4] firmware: drop bit ops in favor of simple state machine

From: Daniel Wagner <daniel.wagner@...-carit.de>

We track the state of the firmware loading with bit ops.  Since the
state machine has only a few states and they are all mutual exclusive
there are only a few simple state transition we can model this simplify.

	   UNKNOWN -> LOADING -> DONE | ABORTED

Because we don't use any bit ops on fw_state::status anymore we are able
to change the data type to enum fw_status and update the function
arguments accordingly.

READ_ONCE() and WRITE_ONCE() are propably not needed because there are a
lot of load and stores around fw_st->status. But let's make it explicit
and not be sorry later.

Cc: Ming Lei <ming.lei@...onical.com>
Cc: Luis R. Rodriguez <mcgrof@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Daniel Wagner <daniel.wagner@...-carit.de>
---
 drivers/base/firmware_class.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index d3b614d10d60..1fda674f5219 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -112,7 +112,7 @@ static inline long firmware_loading_timeout(void)
  */
 struct fw_state {
 	struct completion completion;
-	unsigned long status;
+	enum fw_status status;
 };
 
 static void fw_state_init(struct fw_state *fw_st)
@@ -123,7 +123,7 @@ static void fw_state_init(struct fw_state *fw_st)
 
 static int __fw_state_check(struct fw_state *fw_st, enum fw_status status)
 {
-	return test_bit(status, &fw_st->status);
+	return fw_st->status == status;
 }
 
 static long __fw_state_wait_common(struct fw_state *fw_st, long timeout)
@@ -132,7 +132,7 @@ static long __fw_state_wait_common(struct fw_state *fw_st, long timeout)
 
 	ret = wait_for_completion_interruptible_timeout(&fw_st->completion,
 							timeout);
-	if (ret != 0 && test_bit(FW_STATUS_ABORTED, &fw_st->status))
+	if (ret != 0 && READ_ONCE(fw_st->status) == FW_STATUS_ABORTED)
 		return -ENOENT;
 
 	return ret;
@@ -141,12 +141,10 @@ static long __fw_state_wait_common(struct fw_state *fw_st, long timeout)
 static void __fw_state_set(struct fw_state *fw_st,
 			   enum fw_status status)
 {
-	set_bit(status, &fw_st->status);
+	WRITE_ONCE(fw_st->status, status);
 
-	if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED) {
-		clear_bit(FW_STATUS_LOADING, &fw_st->status);
+	if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED)
 		complete_all(&fw_st->completion);
-	}
 }
 
 #define fw_state_start(fw_st)					\
-- 
2.7.4