media: core: add ov_16bit_addr_reg_helpers.h

The following drivers under drivers/media/i2c: ov08x40.c, ov13858.c,
ov13b10.c, ov2680.c, ov2685.c, ov2740.c, ov4689.c, ov5670.c,
ov5675.c, ov5695.c, ov8856.c, ov9282.c and ov9734.c,

as well as various "atomisp" sensor drivers in drivers/staging, *all*
use register access helpers with the following function prototypes:

int ovxxxx_read_reg(struct ovxxxx_dev *sensor, u16 reg,
                    unsigned int len, u32 *val);

int ovxxxx_write_reg(struct ovxxxx_dev *sensor, u16 reg,
                     unsigned int len, u32 val);

To read/write registers on Omnivision OVxxxx image sensors wich expect
a 16 bit register address in big-endian format and which have 1-3 byte
wide registers, in big-endian format (for the higher width registers).

Add a new ov_16bit_addr_reg_helpers.h header file with static inline
versions of these register access helpers, so that this code duplication
can be removed.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

include/media/ov_16bit_addr_reg_helpers.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * I2C register access helpers for Omnivision OVxxxx image sensors which expect
+ * a 16 bit register address in big-endian format and which have 1-3 byte
+ * wide registers, in big-endian format (for the higher width registers).
+ *
+ * Based on the register helpers from drivers/media/i2c/ov2680.c which is:
+ * Copyright (C) 2018 Linaro Ltd
+ */
+#ifndef __OV_16BIT_ADDR_REG_HELPERS_H
+#define __OV_16BIT_ADDR_REG_HELPERS_H
+
+#include <asm/unaligned.h>
+#include <linux/dev_printk.h>
+#include <linux/i2c.h>
+
+static inline int ov_read_reg(struct i2c_client *client, u16 reg,
+				  unsigned int len, u32 *val)
+{
+	u8 addr_buf[2], data_buf[4] = { };
+	struct i2c_msg msgs[2];
+	int ret;
+
+	if (len > 4)
+		return -EINVAL;
+
+	put_unaligned_be16(reg, addr_buf);
+
+	msgs[0].addr = client->addr;
+	msgs[0].flags = 0;
+	msgs[0].len = ARRAY_SIZE(addr_buf);
+	msgs[0].buf = addr_buf;
+
+	msgs[1].addr = client->addr;
+	msgs[1].flags = I2C_M_RD;
+	msgs[1].len = len;
+	msgs[1].buf = &data_buf[4 - len];
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "read error: reg=0x%4x: %d\n", reg, ret);
+		return -EIO;
+	}
+
+	*val = get_unaligned_be32(data_buf);
+
+	return 0;
+}
+
+#define ov_read_reg8(s, r, v)	ov_read_reg(s, r, 1, v)
+#define ov_read_reg16(s, r, v)	ov_read_reg(s, r, 2, v)
+#define ov_read_reg24(s, r, v)	ov_read_reg(s, r, 3, v)
+
+static inline int ov_write_reg(struct i2c_client *client, u16 reg,
+				   unsigned int len, u32 val)
+{
+	u8 buf[6];
+	int ret;
+
+	if (len > 4)
+		return -EINVAL;
+
+	put_unaligned_be16(reg, buf);
+	put_unaligned_be32(val << (8 * (4 - len)), buf + 2);
+	ret = i2c_master_send(client, buf, len + 2);
+	if (ret != len + 2) {
+		dev_err(&client->dev, "write error: reg=0x%4x: %d\n", reg, ret);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+#define ov_write_reg8(s, r, v)	ov_write_reg(s, r, 1, v)
+#define ov_write_reg16(s, r, v)	ov_write_reg(s, r, 2, v)
+#define ov_write_reg24(s, r, v)	ov_write_reg(s, r, 3, v)
+
+static inline int ov_update_reg(struct i2c_client *client, u16 reg, u8 mask, u8 val)
+{
+	u32 readval;
+	int ret;
+
+	ret = ov_read_reg8(client, reg, &readval);
+	if (ret < 0)
+		return ret;
+
+	val = (readval & ~mask) | (val & mask);
+
+	return ov_write_reg8(client, reg, val);
+}
+
+#endif