i2c-stub: Chip address as a module parameter

i2c-stub: Chip address as a module parameter

Add a mandatory chip_addr parameter to i2c-stub. This parameter
defines to which chip address the driver will respond, instead of
reponding to all addresses as before. The idea is to prevent the
users from loading i2c-stub at random and being then confused by
the results of sensors-detect or other user-space tools.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub
index d6dcb138abf510534d2539665f74176c013a37b4..9cc081e697648ecb3feaadddcc4b8da187294db9 100644 (file)
--- a/Documentation/i2c/i2c-stub
+++ b/Documentation/i2c/i2c-stub
@@ -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.
 
 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
 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
 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
 
        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
 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.
 
 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.
 
 If you spam it hard enough, printk can be lossy.  This module really wants
 something like relayfs.
 

diff --git a/drivers/i2c/busses/i2c-stub.c b/drivers/i2c/busses/i2c-stub.c
index 73f481e93a36458c3040e391d3a16ac649d9affd..8cf374ddd98917481bfae7720b11b60c547d2b7e 100644 (file)
--- a/drivers/i2c/busses/i2c-stub.c
+++ b/drivers/i2c/busses/i2c-stub.c
@@ -27,6 +27,10 @@
 #include <linux/errno.h>
 #include <linux/i2c.h>
 
 #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];
 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;
 
 {
        s32 ret;
 

+       if (addr != chip_addr)
+               return -ENODEV;
+

        switch (size) {
 
        case I2C_SMBUS_QUICK:
        switch (size) {
 
        case I2C_SMBUS_QUICK:


@@ -122,7 +129,17 @@ static struct i2c_adapter stub_adapter = {
 
 static int __init i2c_stub_init(void)
 {
 
 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);
 }
 
        return i2c_add_adapter(&stub_adapter);
 }