i2c-stub: Chip address as a module parameter (7a8d29ce) · Commits · 戴 / test

Documentation/i2c/i2c-stub

+13 −2

Original line number	Diff line number	Diff line
		@@ -6,9 +6,12 @@ This module is a very simple fake I2C/SMBus driver. It implements four
		types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, and
		(r/w) word data.

		You need to provide a chip address as a module parameter when loading
		this driver, which will then only react to SMBus commands to this address.

		No hardware is needed nor associated with this module. It will accept write
		quick commands to all addresses; it will respond to the other commands (also
		to all addresses) by reading from or writing to an array in memory. It will
		quick commands to one address; it will respond to the other commands (also
		to one address) by reading from or writing to an array in memory. It will
		also spam the kernel logs for every command it handles.

		A pointer register with auto-increment is implemented for all byte
		@@ -21,6 +24,11 @@ The typical use-case is like this:
		3. load the target sensors chip driver module
		4. observe its behavior in the kernel log

		PARAMETERS:

		int chip_addr:
		The SMBus address to emulate a chip at.

		CAVEATS:

		There are independent arrays for byte/data and word/data commands. Depending
		@@ -33,6 +41,9 @@ If the hardware for your driver has banked registers (e.g. Winbond sensors
		chips) this module will not work well - although it could be extended to
		support that pretty easily.

		Only one chip address is supported - although this module could be
		extended to support more.

		If you spam it hard enough, printk can be lossy. This module really wants
		something like relayfs.

drivers/i2c/busses/i2c-stub.c

+18 −1

Original line number	Diff line number	Diff line
		@@ -27,6 +27,10 @@
		#include <linux/errno.h>
		#include <linux/i2c.h>

		static unsigned short chip_addr;
		module_param(chip_addr, ushort, S_IRUGO);
		MODULE_PARM_DESC(chip_addr, "Chip address (between 0x03 and 0x77)\n");

		static u8 stub_pointer;
		static u8 stub_bytes[256];
		static u16 stub_words[256];
		@@ -37,6 +41,9 @@ static s32 stub_xfer(struct i2c_adapter * adap, u16 addr, unsigned short flags,
		{
		s32 ret;

		if (addr != chip_addr)
		return -ENODEV;

		switch (size) {

		case I2C_SMBUS_QUICK:
		@@ -122,7 +129,17 @@ static struct i2c_adapter stub_adapter = {

		static int __init i2c_stub_init(void)
		{
		printk(KERN_INFO "i2c-stub loaded\n");
		if (!chip_addr) {
		printk(KERN_ERR "i2c-stub: Please specify a chip address\n");
		return -ENODEV;
		}
		if (chip_addr < 0x03 \|\| chip_addr > 0x77) {
		printk(KERN_ERR "i2c-stub: Invalid chip address 0x%02x\n",
		chip_addr);
		return -EINVAL;
		}

		printk(KERN_INFO "i2c-stub: Virtual chip at 0x%02x\n", chip_addr);
		return i2c_add_adapter(&stub_adapter);
		}

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