netdev - [PATCH 03/28] mfd: zl3073x: Add register access helpers

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Message-ID: <20250407172836.1009461-4-ivecera@redhat.com>
Date: Mon,  7 Apr 2025 19:28:30 +0200
From: Ivan Vecera <ivecera@...hat.com>
To: netdev@...r.kernel.org
Cc: Michal Schmidt <mschmidt@...hat.com>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Prathosh Satish <Prathosh.Satish@...rochip.com>,
	Lee Jones <lee@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Andy Shevchenko <andy@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH 03/28] mfd: zl3073x: Add register access helpers

Add helpers zl3073x_{read,write}_reg() to access device registers.
These functions have to be called with device lock that can be taken
by zl3073x_{lock,unlock}() or a caller can use defined guard.

Reviewed-by: Michal Schmidt <mschmidt@...hat.com>
Signed-off-by: Ivan Vecera <ivecera@...hat.com>
---
 drivers/mfd/zl3073x-core.c  | 88 +++++++++++++++++++++++++++++++++++++
 include/linux/mfd/zl3073x.h | 32 ++++++++++++++
 2 files changed, 120 insertions(+)

diff --git a/drivers/mfd/zl3073x-core.c b/drivers/mfd/zl3073x-core.c
index 71454f683eab0..39d4c8608a740 100644
--- a/drivers/mfd/zl3073x-core.c
+++ b/drivers/mfd/zl3073x-core.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
 #include <linux/module.h>
+#include <linux/unaligned.h>
 #include <net/devlink.h>
 #include "zl3073x.h"
 
@@ -45,6 +46,93 @@ const struct regmap_config *zl3073x_get_regmap_config(void)
 }
 EXPORT_SYMBOL_NS_GPL(zl3073x_get_regmap_config, "ZL3073X");
 
+/**
+ * zl3073x_read_reg - Read value from device register
+ * @zldev: device structure pointer
+ * @reg: register to be read
+ * @len: number of bytes to read
+ * @value: pointer to place to store value read from the register
+ *
+ * Caller has to hold the device lock that can be obtained
+ * by zl3073x_lock().
+ *
+ * Returns 0 in case of success or negative value otherwise
+ */
+int zl3073x_read_reg(struct zl3073x_dev *zldev, unsigned int reg,
+		     unsigned int len, void *value)
+{
+	u8 buf[6];
+	int rc;
+
+	lockdep_assert_held(&zldev->lock);
+
+	rc = regmap_bulk_read(zldev->regmap, reg, buf, len);
+	if (rc)
+		return rc;
+
+	switch (len) {
+	case 1:
+		*(u8 *)value = buf[0];
+		break;
+	case 2:
+		*(u16 *)value = get_unaligned_be16(buf);
+		break;
+	case 4:
+		*(u32 *)value = get_unaligned_be32(buf);
+		break;
+	case 6:
+		*(u64 *)value = get_unaligned_be48(buf);
+		break;
+	default:
+		WARN(true, "Unsupported register size: %u\n", len);
+		break;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(zl3073x_read_reg);
+
+/**
+ * zl3073x_write_reg - Write value to device register
+ * @zldev: device structure pointer
+ * @reg: register to be written
+ * @len: number of bytes to write
+ * @value: pointer to value to write to the register
+ *
+ * Caller has to hold the device lock that can be obtained
+ * by zl3073x_lock().
+ *
+ * Returns 0 in case of success or negative value otherwise
+ */
+int zl3073x_write_reg(struct zl3073x_dev *zldev, unsigned int reg,
+		      unsigned int len, const void *value)
+{
+	u8 buf[6];
+
+	lockdep_assert_held(&zldev->lock);
+
+	switch (len) {
+	case 1:
+		buf[0] = *(u8 *)value;
+		break;
+	case 2:
+		put_unaligned_be16(*(u16 *)value, buf);
+		break;
+	case 4:
+		put_unaligned_be32(*(u32 *)value, buf);
+		break;
+	case 6:
+		put_unaligned_be48(*(u64 *)value, buf);
+		break;
+	default:
+		WARN(true, "Unsupported register size: %u\n", len);
+		break;
+	}
+
+	return regmap_bulk_write(zldev->regmap, reg, buf, len);
+}
+EXPORT_SYMBOL_GPL(zl3073x_write_reg);
+
 static const struct devlink_ops zl3073x_devlink_ops = {
 };
 
diff --git a/include/linux/mfd/zl3073x.h b/include/linux/mfd/zl3073x.h
index 7b80c3059b5f3..0156f9044d79d 100644
--- a/include/linux/mfd/zl3073x.h
+++ b/include/linux/mfd/zl3073x.h
@@ -12,4 +12,36 @@ struct zl3073x_dev {
 	struct mutex		lock;
 };
 
+/**
+ * zl3073x_lock - Lock the device
+ * @zldev: device structure pointer
+ *
+ * Caller has to take this lock when it needs to access device registers.
+ */
+static inline void zl3073x_lock(struct zl3073x_dev *zldev)
+{
+	mutex_lock(&zldev->lock);
+}
+
+/**
+ * zl3073x_unlock - Unlock the device
+ * @zldev: device structure pointer
+ *
+ * Caller unlocks the device when it does not need to access device
+ * registers anymore.
+ */
+static inline void zl3073x_unlock(struct zl3073x_dev *zldev)
+{
+	mutex_unlock(&zldev->lock);
+}
+
+DEFINE_GUARD(zl3073x, struct zl3073x_dev *, zl3073x_lock(_T),
+	     zl3073x_unlock(_T));
+
+int zl3073x_read_reg(struct zl3073x_dev *zldev, unsigned int reg,
+		     unsigned int len, void *value);
+
+int zl3073x_write_reg(struct zl3073x_dev *zldev, unsigned int reg,
+		      unsigned int len, const void *value);
+
 #endif /* __LINUX_MFD_ZL3073X_H */
-- 
2.48.1