// 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);