[PATCH 01/10] ASoC: cirrus: Add helper function for reading the device ID

[Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>]

Many of the older Cirrus devices share very similar code for reading the
device ID, and frequently this code is generating cppcheck warnings such
as:

sound/soc/codecs/cs42l42.c:1886:6: style: Variable 'ret' is reassigned
a value before the old one has been used. [redundantAssignment]
 ret = regmap_read(cs42l42->regmap, CS42L42_DEVID_CD, &reg);

Add a small helper function that older Cirrus devices can use to read
the device ID, which should help correct these issues.

Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
Signed-off-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
---
 sound/soc/codecs/cirrus_legacy.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 sound/soc/codecs/cirrus_legacy.h

diff --git a/sound/soc/codecs/cirrus_legacy.h b/sound/soc/codecs/cirrus_legacy.h
new file mode 100644
index 0000000000000..87c6fd79290d4
--- /dev/null
+++ b/sound/soc/codecs/cirrus_legacy.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Some small helpers for older Cirrus Logic parts.
+ *
+ * Copyright (C) 2021 Cirrus Logic, Inc. and
+ *                    Cirrus Logic International Semiconductor Ltd.
+ */
+
+static inline int cirrus_read_device_id(struct regmap *regmap, unsigned int reg)
+{
+	u8 devid[3];
+	int ret;
+
+	ret = regmap_bulk_read(regmap, reg, devid, ARRAY_SIZE(devid));
+	if (ret < 0)
+		return ret;
+
+	return ((devid[0] & 0xFF) << 12) |
+	       ((devid[1] & 0xFF) <<  4) |
+	       ((devid[2] & 0xF0) >>  4);
+}
-- 
2.11.0