1 files changed, 414 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-stub.c b/drivers/i2c/i2c-stub.c
new file mode 100644
index 000000000..537a598e2
--- /dev/null
+++ b/drivers/i2c/i2c-stub.c
@@ -0,0 +1,414 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+    i2c-stub.c - I2C/SMBus chip emulator
+
+    Copyright (c) 2004 Mark M. Hoffman <mhoffman@lightlink.com>
+    Copyright (C) 2007-2014 Jean Delvare <jdelvare@suse.de>
+
+*/
+
+#define DEBUG 1
+#define pr_fmt(fmt) "i2c-stub: " fmt
+
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#define MAX_CHIPS 10
+
+/*
+ * Support for I2C_FUNC_SMBUS_BLOCK_DATA is disabled by default and must
+ * be enabled explicitly by setting the I2C_FUNC_SMBUS_BLOCK_DATA bits
+ * in the 'functionality' module parameter.
+ */
+#define STUB_FUNC_DEFAULT \
+		(I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \
+		 I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
+		 I2C_FUNC_SMBUS_I2C_BLOCK)
+
+#define STUB_FUNC_ALL \
+		(STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA)
+
+static unsigned short chip_addr[MAX_CHIPS];
+module_param_array(chip_addr, ushort, NULL, S_IRUGO);
+MODULE_PARM_DESC(chip_addr,
+		 "Chip addresses (up to 10, between 0x03 and 0x77)");
+
+static unsigned long functionality = STUB_FUNC_DEFAULT;
+module_param(functionality, ulong, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(functionality, "Override functionality bitfield");
+
+/* Some chips have banked register ranges */
+
+static u8 bank_reg[MAX_CHIPS];
+module_param_array(bank_reg, byte, NULL, S_IRUGO);
+MODULE_PARM_DESC(bank_reg, "Bank register");
+
+static u8 bank_mask[MAX_CHIPS];
+module_param_array(bank_mask, byte, NULL, S_IRUGO);
+MODULE_PARM_DESC(bank_mask, "Bank value mask");
+
+static u8 bank_start[MAX_CHIPS];
+module_param_array(bank_start, byte, NULL, S_IRUGO);
+MODULE_PARM_DESC(bank_start, "First banked register");
+
+static u8 bank_end[MAX_CHIPS];
+module_param_array(bank_end, byte, NULL, S_IRUGO);
+MODULE_PARM_DESC(bank_end, "Last banked register");
+
+struct smbus_block_data {
+	struct list_head node;
+	u8 command;
+	u8 len;
+	u8 block[I2C_SMBUS_BLOCK_MAX];
+};
+
+struct stub_chip {
+	u8 pointer;
+	u16 words[256];		/* Byte operations use the LSB as per SMBus
+				   specification */
+	struct list_head smbus_blocks;
+
+	/* For chips with banks, extra registers are allocated dynamically */
+	u8 bank_reg;
+	u8 bank_shift;
+	u8 bank_mask;
+	u8 bank_sel;		/* Currently selected bank */
+	u8 bank_start;
+	u8 bank_end;
+	u16 bank_size;
+	u16 *bank_words;	/* Room for bank_mask * bank_size registers */
+};
+
+static struct stub_chip *stub_chips;
+static int stub_chips_nr;
+
+static struct smbus_block_data *stub_find_block(struct device *dev,
+						struct stub_chip *chip,
+						u8 command, bool create)
+{
+	struct smbus_block_data *b, *rb = NULL;
+
+	list_for_each_entry(b, &chip->smbus_blocks, node) {
+		if (b->command == command) {
+			rb = b;
+			break;
+		}
+	}
+	if (rb == NULL && create) {
+		rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL);
+		if (rb == NULL)
+			return rb;
+		rb->command = command;
+		list_add(&rb->node, &chip->smbus_blocks);
+	}
+	return rb;
+}
+
+static u16 *stub_get_wordp(struct stub_chip *chip, u8 offset)
+{
+	if (chip->bank_sel &&
+	    offset >= chip->bank_start && offset <= chip->bank_end)
+		return chip->bank_words +
+		       (chip->bank_sel - 1) * chip->bank_size +
+		       offset - chip->bank_start;
+	else
+		return chip->words + offset;
+}
+
+/* Return negative errno on error. */
+static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
+	char read_write, u8 command, int size, union i2c_smbus_data *data)
+{
+	s32 ret;
+	int i, len;
+	struct stub_chip *chip = NULL;
+	struct smbus_block_data *b;
+	u16 *wordp;
+
+	/* Search for the right chip */
+	for (i = 0; i < stub_chips_nr; i++) {
+		if (addr == chip_addr[i]) {
+			chip = stub_chips + i;
+			break;
+		}
+	}
+	if (!chip)
+		return -ENODEV;
+
+	switch (size) {
+
+	case I2C_SMBUS_QUICK:
+		dev_dbg(&adap->dev, "smbus quick - addr 0x%02x\n", addr);
+		ret = 0;
+		break;
+
+	case I2C_SMBUS_BYTE:
+		if (read_write == I2C_SMBUS_WRITE) {
+			chip->pointer = command;
+			dev_dbg(&adap->dev,
+				"smbus byte - addr 0x%02x, wrote 0x%02x.\n",
+				addr, command);
+		} else {
+			wordp = stub_get_wordp(chip, chip->pointer++);
+			data->byte = *wordp & 0xff;
+			dev_dbg(&adap->dev,
+				"smbus byte - addr 0x%02x, read  0x%02x.\n",
+				addr, data->byte);
+		}
+
+		ret = 0;
+		break;
+
+	case I2C_SMBUS_BYTE_DATA:
+		wordp = stub_get_wordp(chip, command);
+		if (read_write == I2C_SMBUS_WRITE) {
+			*wordp &= 0xff00;
+			*wordp |= data->byte;
+			dev_dbg(&adap->dev,
+				"smbus byte data - addr 0x%02x, wrote 0x%02x at 0x%02x.\n",
+				addr, data->byte, command);
+
+			/* Set the bank as needed */
+			if (chip->bank_words && command == chip->bank_reg) {
+				chip->bank_sel =
+					(data->byte >> chip->bank_shift)
+					& chip->bank_mask;
+				dev_dbg(&adap->dev,
+					"switching to bank %u.\n",
+					chip->bank_sel);
+			}
+		} else {
+			data->byte = *wordp & 0xff;
+			dev_dbg(&adap->dev,
+				"smbus byte data - addr 0x%02x, read  0x%02x at 0x%02x.\n",
+				addr, data->byte, command);
+		}
+		chip->pointer = command + 1;
+
+		ret = 0;
+		break;
+
+	case I2C_SMBUS_WORD_DATA:
+		wordp = stub_get_wordp(chip, command);
+		if (read_write == I2C_SMBUS_WRITE) {
+			*wordp = data->word;
+			dev_dbg(&adap->dev,
+				"smbus word data - addr 0x%02x, wrote 0x%04x at 0x%02x.\n",
+				addr, data->word, command);
+		} else {
+			data->word = *wordp;
+			dev_dbg(&adap->dev,
+				"smbus word data - addr 0x%02x, read  0x%04x at 0x%02x.\n",
+				addr, data->word, command);
+		}
+
+		ret = 0;
+		break;
+
+	case I2C_SMBUS_I2C_BLOCK_DATA:
+		/*
+		 * We ignore banks here, because banked chips don't use I2C
+		 * block transfers
+		 */
+		if (data->block[0] > 256 - command)	/* Avoid overrun */
+			data->block[0] = 256 - command;
+		len = data->block[0];
+		if (read_write == I2C_SMBUS_WRITE) {
+			for (i = 0; i < len; i++) {
+				chip->words[command + i] &= 0xff00;
+				chip->words[command + i] |= data->block[1 + i];
+			}
+			dev_dbg(&adap->dev,
+				"i2c block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
+				addr, len, command);
+		} else {
+			for (i = 0; i < len; i++) {
+				data->block[1 + i] =
+					chip->words[command + i] & 0xff;
+			}
+			dev_dbg(&adap->dev,
+				"i2c block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
+				addr, len, command);
+		}
+
+		ret = 0;
+		break;
+
+	case I2C_SMBUS_BLOCK_DATA:
+		/*
+		 * We ignore banks here, because chips typically don't use both
+		 * banks and SMBus block transfers
+		 */
+		b = stub_find_block(&adap->dev, chip, command, false);
+		if (read_write == I2C_SMBUS_WRITE) {
+			len = data->block[0];
+			if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) {
+				ret = -EINVAL;
+				break;
+			}
+			if (b == NULL) {
+				b = stub_find_block(&adap->dev, chip, command,
+						    true);
+				if (b == NULL) {
+					ret = -ENOMEM;
+					break;
+				}
+			}
+			/* Largest write sets read block length */
+			if (len > b->len)
+				b->len = len;
+			for (i = 0; i < len; i++)
+				b->block[i] = data->block[i + 1];
+			/* update for byte and word commands */
+			chip->words[command] = (b->block[0] << 8) | b->len;
+			dev_dbg(&adap->dev,
+				"smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n",
+				addr, len, command);
+		} else {
+			if (b == NULL) {
+				dev_dbg(&adap->dev,
+					"SMBus block read command without prior block write not supported\n");
+				ret = -EOPNOTSUPP;
+				break;
+			}
+			len = b->len;
+			data->block[0] = len;
+			for (i = 0; i < len; i++)
+				data->block[i + 1] = b->block[i];
+			dev_dbg(&adap->dev,
+				"smbus block data - addr 0x%02x, read  %d bytes at 0x%02x.\n",
+				addr, len, command);
+		}
+
+		ret = 0;
+		break;
+
+	default:
+		dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
+		ret = -EOPNOTSUPP;
+		break;
+	} /* switch (size) */
+
+	return ret;
+}
+
+static u32 stub_func(struct i2c_adapter *adapter)
+{
+	return STUB_FUNC_ALL & functionality;
+}
+
+static const struct i2c_algorithm smbus_algorithm = {
+	.functionality	= stub_func,
+	.smbus_xfer	= stub_xfer,
+};
+
+static struct i2c_adapter stub_adapter = {
+	.owner		= THIS_MODULE,
+	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
+	.algo		= &smbus_algorithm,
+	.name		= "SMBus stub driver",
+};
+
+static int __init i2c_stub_allocate_banks(int i)
+{
+	struct stub_chip *chip = stub_chips + i;
+
+	chip->bank_reg = bank_reg[i];
+	chip->bank_start = bank_start[i];
+	chip->bank_end = bank_end[i];
+	chip->bank_size = bank_end[i] - bank_start[i] + 1;
+
+	/* We assume that all bits in the mask are contiguous */
+	chip->bank_mask = bank_mask[i];
+	while (!(chip->bank_mask & 1)) {
+		chip->bank_shift++;
+		chip->bank_mask >>= 1;
+	}
+
+	chip->bank_words = kcalloc(chip->bank_mask * chip->bank_size,
+				   sizeof(u16),
+				   GFP_KERNEL);
+	if (!chip->bank_words)
+		return -ENOMEM;
+
+	pr_debug("Allocated %u banks of %u words each (registers 0x%02x to 0x%02x)\n",
+		 chip->bank_mask, chip->bank_size, chip->bank_start,
+		 chip->bank_end);
+
+	return 0;
+}
+
+static void i2c_stub_free(void)
+{
+	int i;
+
+	for (i = 0; i < stub_chips_nr; i++)
+		kfree(stub_chips[i].bank_words);
+	kfree(stub_chips);
+}
+
+static int __init i2c_stub_init(void)
+{
+	int i, ret;
+
+	if (!chip_addr[0]) {
+		pr_err("Please specify a chip address\n");
+		return -ENODEV;
+	}
+
+	for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
+		if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
+			pr_err("Invalid chip address 0x%02x\n",
+			       chip_addr[i]);
+			return -EINVAL;
+		}
+
+		pr_info("Virtual chip at 0x%02x\n", chip_addr[i]);
+	}
+
+	/* Allocate memory for all chips at once */
+	stub_chips_nr = i;
+	stub_chips = kcalloc(stub_chips_nr, sizeof(struct stub_chip),
+			     GFP_KERNEL);
+	if (!stub_chips)
+		return -ENOMEM;
+
+	for (i = 0; i < stub_chips_nr; i++) {
+		INIT_LIST_HEAD(&stub_chips[i].smbus_blocks);
+
+		/* Allocate extra memory for banked register ranges */
+		if (bank_mask[i]) {
+			ret = i2c_stub_allocate_banks(i);
+			if (ret)
+				goto fail_free;
+		}
+	}
+
+	ret = i2c_add_adapter(&stub_adapter);
+	if (ret)
+		goto fail_free;
+
+	return 0;
+
+ fail_free:
+	i2c_stub_free();
+	return ret;
+}
+
+static void __exit i2c_stub_exit(void)
+{
+	i2c_del_adapter(&stub_adapter);
+	i2c_stub_free();
+}
+
+MODULE_AUTHOR("Mark M. Hoffman <mhoffman@lightlink.com>");
+MODULE_DESCRIPTION("I2C stub driver");
+MODULE_LICENSE("GPL");
+
+module_init(i2c_stub_init);
+module_exit(i2c_stub_exit);