From: Jean Delvare <khali@xxxxxxxxxxxx>
Subject: i2c-stub: Add support for bus multiplexing
Emulate a PCA9540 mux chip on request. There are two reasons for
implementing this:
* This makes it possible to emulate two chips at the same address.
* This lets us test the multiplexing code.
Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
Cc: Michael Lawnick <ml.lawnick@xxxxxx>
Cc: Rodolfo Giometti <giometti@xxxxxxxxxxxx>
---
Documentation/i2c/i2c-stub | 9 ++
drivers/i2c/busses/i2c-stub.c | 179 +++++++++++++++++++++++++++++++++++++----
2 files changed, 171 insertions(+), 17 deletions(-)
--- linux-2.6.34-rc5.orig/drivers/i2c/busses/i2c-stub.c 2010-04-20 08:18:24.000000000 +0200
+++ linux-2.6.34-rc5/drivers/i2c/busses/i2c-stub.c 2010-04-20 13:42:53.000000000 +0200
@@ -2,7 +2,7 @@
i2c-stub.c - I2C/SMBus chip emulator
Copyright (c) 2004 Mark M. Hoffman <mhoffman@xxxxxxxxxxxxx>
- Copyright (C) 2007 Jean Delvare <khali@xxxxxxxxxxxx>
+ Copyright (C) 2007-2010 Jean Delvare <khali@xxxxxxxxxxxx>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -33,11 +33,26 @@
I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \
I2C_FUNC_SMBUS_I2C_BLOCK)
+#define PCA9540_ADDR 0x70
+#define PCA9540_CHAN_MASK 0x07
+#define PCA9540_CHAN0_EN 0x04
+#define PCA9540_CHAN1_EN 0x05
+
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 short pca9540_addr_0[MAX_CHIPS];
+module_param_array(pca9540_addr_0, ushort, NULL, S_IRUGO);
+MODULE_PARM_DESC(pca9540_addr_0,
+ "Chip addresses on PCA9540 mux branch 0 (up to 10)");
+
+static unsigned short pca9540_addr_1[MAX_CHIPS];
+module_param_array(pca9540_addr_1, ushort, NULL, S_IRUGO);
+MODULE_PARM_DESC(pca9540_addr_1,
+ "Chip addresses on PCA9540 mux branch 1 (up to 10)");
+
static unsigned long functionality = STUB_FUNC;
module_param(functionality, ulong, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(functionality, "Override functionality bitfield");
@@ -49,10 +64,41 @@ struct stub_chip {
};
static struct stub_chip *stub_chips;
+static struct stub_chip *pca9540_chips_0;
+static struct stub_chip *pca9540_chips_1;
+static int have_pca9540;
+static u8 pca9540_state;
+
+static struct stub_chip *pca9540_get_chip(u16 addr)
+{
+ const unsigned short *pca9540_addr;
+ struct stub_chip *pca9540_chips;
+ int i;
+
+ switch (pca9540_state & PCA9540_CHAN_MASK) {
+ case PCA9540_CHAN0_EN:
+ pca9540_addr = pca9540_addr_0;
+ pca9540_chips = pca9540_chips_0;
+ break;
+ case PCA9540_CHAN1_EN:
+ pca9540_addr = pca9540_addr_1;
+ pca9540_chips = pca9540_chips_1;
+ break;
+ default:
+ return NULL;
+ }
+
+ for (i = 0; i < MAX_CHIPS && pca9540_addr[i]; i++) {
+ if (addr == pca9540_addr[i])
+ return pca9540_chips + i;
+ }
+ return NULL;
+}
/* 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)
+static s32 stub_xfer_normal(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;
@@ -65,6 +111,19 @@ static s32 stub_xfer(struct i2c_adapter
break;
}
}
+ /* If a PCA9540 mux chip is emulated, check its state to find out
+ * which devices are reachable */
+ if (have_pca9540) {
+ struct stub_chip *chip_muxed = pca9540_get_chip(addr);
+ if (chip_muxed) {
+ if (chip) {
+ dev_err(&adap->dev, "Bad bus topology, "
+ "duplicate address 0x%02x\n", addr);
+ return -EIO;
+ }
+ chip = chip_muxed;
+ }
+ }
if (!chip)
return -ENODEV;
@@ -157,6 +216,39 @@ static s32 stub_xfer(struct i2c_adapter
return ret;
}
+/* Emulate a PCA9540 mux chip */
+static s32 stub_xfer_pca9540(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write, u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ if (size != I2C_SMBUS_BYTE) {
+ dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n");
+ return -EOPNOTSUPP;
+ }
+
+ if (read_write == I2C_SMBUS_WRITE) {
+ pca9540_state = command;
+ dev_dbg(&adap->dev, "PCA9540 - set to 0x%02x.\n", command);
+ } else {
+ data->byte = pca9540_state;
+ dev_dbg(&adap->dev, "PCA9540 - read 0x%02x.\n", data->byte);
+ }
+
+ return 0;
+}
+
+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)
+{
+ if (have_pca9540 && addr == PCA9540_ADDR) {
+ return stub_xfer_pca9540(adap, addr, flags, read_write,
+ command, size, data);
+ } else {
+ return stub_xfer_normal(adap, addr, flags, read_write,
+ command, size, data);
+ }
+}
+
static u32 stub_func(struct i2c_adapter *adapter)
{
return STUB_FUNC & functionality;
@@ -174,36 +266,89 @@ static struct i2c_adapter stub_adapter =
.name = "SMBus stub driver",
};
-static int __init i2c_stub_init(void)
+static int __init i2c_stub_parse_addresses(const unsigned short *addr,
+ struct stub_chip **chipsp, const char *suffix)
{
- int i, ret;
+ int i;
- if (!chip_addr[0]) {
- printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
- return -ENODEV;
- }
+ /* Nothing to do if the address list is empty */
+ if (!addr[0])
+ return 0;
- for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) {
- if (chip_addr[i] < 0x03 || chip_addr[i] > 0x77) {
+ for (i = 0; i < MAX_CHIPS && addr[i]; i++) {
+ if (addr[i] < 0x03 || addr[i] > 0x77) {
printk(KERN_ERR "i2c-stub: Invalid chip address "
- "0x%02x\n", chip_addr[i]);
+ "0x%02x\n", addr[i]);
+ return -EINVAL;
+ }
+ if (have_pca9540 && addr[i] == PCA9540_ADDR) {
+ printk(KERN_ERR "i2c-stub: Address 0x%02x reserved "
+ "for PCA9540 mux\n", addr[i]);
return -EINVAL;
}
- printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n",
- chip_addr[i]);
+ printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x%s\n",
+ addr[i], suffix);
}
/* Allocate memory for all chips at once */
- stub_chips = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
- if (!stub_chips) {
+ *chipsp = kzalloc(i * sizeof(struct stub_chip), GFP_KERNEL);
+ if (!*chipsp) {
printk(KERN_ERR "i2c-stub: Out of memory\n");
return -ENOMEM;
}
+ return 0;
+}
+
+static int __init i2c_stub_init(void)
+{
+ int ret;
+
+ have_pca9540 = pca9540_addr_0[0] || pca9540_addr_1[0];
+ if (!chip_addr[0] && !have_pca9540) {
+ printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
+ return -ENODEV;
+ }
+
+ ret = i2c_stub_parse_addresses(chip_addr, &stub_chips, "");
+ if (ret)
+ goto err_free;
+
+ ret = i2c_stub_parse_addresses(pca9540_addr_0, &pca9540_chips_0,
+ " on PCA9540 mux branch 0");
+ if (ret)
+ goto err_free;
+
+ ret = i2c_stub_parse_addresses(pca9540_addr_1, &pca9540_chips_1,
+ " on PCA9540 mux branch 1");
+ if (ret)
+ goto err_free;
+
+ /* Bus multiplexing isn't compatible with device auto-detection */
+ if (have_pca9540)
+ stub_adapter.class = 0;
+
ret = i2c_add_adapter(&stub_adapter);
if (ret)
- kfree(stub_chips);
+ goto err_free;
+
+ /* Instantiate PCA9540 multiplexer chip if requested */
+ if (have_pca9540) {
+ struct i2c_board_info info;
+
+ memset(&info, 0, sizeof(struct i2c_board_info));
+ strlcpy(info.type, "pca9540", I2C_NAME_SIZE);
+ info.addr = PCA9540_ADDR;
+ i2c_new_device(&stub_adapter, &info);
+ }
+
+ return 0;
+
+ err_free:
+ kfree(stub_chips);
+ kfree(pca9540_chips_0);
+ kfree(pca9540_chips_1);
return ret;
}
--- linux-2.6.34-rc5.orig/Documentation/i2c/i2c-stub 2010-03-05 11:08:47.000000000 +0100
+++ linux-2.6.34-rc5/Documentation/i2c/i2c-stub 2010-04-20 14:05:17.000000000 +0200
@@ -33,6 +33,15 @@ PARAMETERS:
int chip_addr[10]:
The SMBus addresses to emulate chips at.
+int pca9540_addr_0[10]:
+int pca9540_addr_1[10]:
+ The SMBus addresses to emulate chips at on the two branches
+ of an emulated PCA9540 mux chip. The PCA9540 chip is emulated
+ at address 0x70 if and only if at least one address is provided
+ for either parameter. Also note that the adapter class is reset
+ in this case, so you always have to explicitly instantiate your
+ devices, auto-detection will no longer work.
+
unsigned long functionality:
Functionality override, to disable some commands. See I2C_FUNC_*
constants in <linux/i2c.h> for the suitable values. For example,
--
Jean Delvare
--
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