Commit a89ba0bc authored by Jean Delvare's avatar Jean Delvare Committed by Greg Kroah-Hartman
Browse files

[PATCH] I2C: Rewrite i2c_probe 

i2c_probe was quite complex and slow, so I rewrote it in a more
efficient and hopefully clearer way.

Note that this slightly changes the way the module parameters are
handled. This shouldn't change anything for the most common cases
though.

For one thing, the function now respects the order of the parameters
for address probing. It used to always do lower addresses first. The
new approach gives the user more control.

For another, ignore addresses don't overrule probe addresses anymore.
This could have been restored the way it was at the cost of a few more
lines of code, but I don't think it's worth it. Both lists are given
as module parameters, so a user would be quite silly to specify the
same addresses in both lists. The normal addresses list is the only
one that isn't controlled by a module parameter, thus is the only one
the user may reasonably want to remove an address from.

Another significant change is the fact that i2c_probe() will no more
stop when a detection function returns -ENODEV. Just because a driver
found a chip it doesn't support isn't a valid reason to stop all
probings for this one driver. This closes the long standing lm_sensors
ticket #1807.

  http://www2.lm-sensors.nu/~lm78/readticket.cgi?ticket=1807



I updated the documentation accordingly.

In terms of algorithmic complexity, the new code is way better. If
I is the ignore address count, P the probe address count, N the
normal address count and F the force address count, the old code
was doing 128 * (F + I + P + N) iterations max, while the new code
does F + P + ((I+1) * N) iterations max. For the most common case
where F, I and P are empty, this is down from 128 * N to N.

Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 3b6c0634

Documentation/i2c/writing-clients

+4 −3
Original line number Diff line number Diff line
@@ -241,9 +241,10 @@ Below, some things are only needed if this is a `sensors' driver. Those 
parts are between /* SENSORS ONLY START */ and /* SENSORS ONLY END */

markers. 



This function should only return an error (any value != 0) if there is

some reason why no more detection should be done anymore. If the

detection just fails for this address, return 0.

Returning an error different from -ENODEV in a detect function will cause

the detection to stop: other addresses and adapters won't be scanned.

This should only be done on fatal or internal errors, such as a memory

shortage or i2c_attach_client failing.



For now, you can ignore the `flags' parameter. It is there for future use.

drivers/i2c/i2c-core.c

+89 −76
Original line number Diff line number Diff line
@@ -662,107 +662,120 @@ int i2c_control(struct i2c_client *client, 
 * Will not work for 10-bit addresses!

 * ----------------------------------------------------

 */

/* Return: kind (>= 0) if force found, -1 if not found */

static inline int i2c_probe_forces(struct i2c_adapter *adapter, int addr,

				   unsigned short **forces)

static int i2c_probe_address(struct i2c_adapter *adapter, int addr, int kind,

			     int (*found_proc) (struct i2c_adapter *, int, int))

{

	unsigned short kind;

	int j, adap_id = i2c_adapter_id(adapter);

	int err;



	for (kind = 0; forces[kind]; kind++) {

		for (j = 0; forces[kind][j] != I2C_CLIENT_END; j += 2) {

			if ((forces[kind][j] == adap_id ||

			     forces[kind][j] == ANY_I2C_BUS)

			 && forces[kind][j + 1] == addr) {

				dev_dbg(&adapter->dev, "found force parameter, "

					"addr 0x%02x, kind %u\n", addr, kind);

				return kind;

			}

		}

	/* Make sure the address is valid */

	if (addr < 0x03 || addr > 0x77) {

		dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",

			 addr);

		return -EINVAL;

	}



	return -1;

	/* Skip if already in use */

	if (i2c_check_addr(adapter, addr))

		return 0;



	/* Make sure there is something at this address, unless forced */

	if (kind < 0

	 && i2c_smbus_xfer(adapter, addr, 0, 0, 0, I2C_SMBUS_QUICK, NULL) < 0)

		return 0;



	/* Finally call the custom detection function */

	err = found_proc(adapter, addr, kind);



	/* -ENODEV can be returned if there is a chip at the given address

	   but it isn't supported by this chip driver. We catch it here as

	   this isn't an error. */

	return (err == -ENODEV) ? 0 : err;

}



int i2c_probe(struct i2c_adapter *adapter,

	      struct i2c_client_address_data *address_data,

	      int (*found_proc) (struct i2c_adapter *, int, int))

{

	int addr,i,found,err;

	int i, err;

	int adap_id = i2c_adapter_id(adapter);



	/* Forget it if we can't probe using SMBUS_QUICK */

	if (! i2c_check_functionality(adapter,I2C_FUNC_SMBUS_QUICK))

		return -1;



	for (addr = 0x00; addr <= 0x7f; addr++) {



		/* Skip if already in use */

		if (i2c_check_addr(adapter,addr))

			continue;



		/* If it is in one of the force entries, we don't do any detection

		   at all */

		found = 0;



	/* Force entries are done first, and are not affected by ignore

	   entries */

	if (address_data->forces) {

			int kind = i2c_probe_forces(adapter, addr,

						    address_data->forces);

			if (kind >= 0) { /* force found */

				if ((err = found_proc(adapter, addr, kind)))

		unsigned short **forces = address_data->forces;

		int kind;



		for (kind = 0; forces[kind]; kind++) {

			for (i = 0; forces[kind][i] != I2C_CLIENT_END;

			     i += 2) {

				if (forces[kind][i] == adap_id

				 || forces[kind][i] == ANY_I2C_BUS) {

					dev_dbg(&adapter->dev, "found force "

						"parameter for adapter %d, "

						"addr 0x%02x, kind %d\n",

						adap_id, forces[kind][i + 1],

						kind);

					err = i2c_probe_address(adapter,

						forces[kind][i + 1],

						kind, found_proc);

					if (err)

						return err;

				continue;

				}

			}



		/* If this address is in one of the ignores, we can forget about

		   it right now */

		for (i = 0;

		     !found && (address_data->ignore[i] != I2C_CLIENT_END);

		     i += 2) {

			if (((adap_id == address_data->ignore[i]) || 

			    ((address_data->ignore[i] == ANY_I2C_BUS))) &&

			    (addr == address_data->ignore[i+1])) {

				dev_dbg(&adapter->dev, "found ignore parameter for adapter %d, "

					"addr %04x\n", adap_id ,addr);

				found = 1;

		}

	}

		if (found) 

			continue;



		/* Now, we will do a detection, but only if it is in the normal or 

		   probe entries */  

		for (i = 0;

		     !found && (address_data->normal_i2c[i] != I2C_CLIENT_END);

		     i += 1) {

			if (addr == address_data->normal_i2c[i]) {

				found = 1;

				dev_dbg(&adapter->dev, "found normal i2c entry for adapter %d, "

					"addr %02x\n", adap_id, addr);

	/* Probe entries are done second, and are not affected by ignore

	   entries either */

	for (i = 0; address_data->probe[i] != I2C_CLIENT_END; i += 2) {

		if (address_data->probe[i] == adap_id

		 || address_data->probe[i] == ANY_I2C_BUS) {

			dev_dbg(&adapter->dev, "found probe parameter for "

				"adapter %d, addr 0x%02x\n", adap_id,

				address_data->probe[i + 1]);

			err = i2c_probe_address(adapter,

						address_data->probe[i + 1],

						-1, found_proc);

			if (err)

				return err;

		}

	}



		for (i = 0;

		     !found && (address_data->probe[i] != I2C_CLIENT_END);

		     i += 2) {

			if (((adap_id == address_data->probe[i]) ||

			    ((address_data->probe[i] == ANY_I2C_BUS))) &&

			    (addr == address_data->probe[i+1])) {

				found = 1;

				dev_dbg(&adapter->dev, "found probe parameter for adapter %d, "

					"addr %04x\n", adap_id,addr);

	/* Normal entries are done last, unless shadowed by an ignore entry */

	for (i = 0; address_data->normal_i2c[i] != I2C_CLIENT_END; i += 1) {

		int j, ignore;



		ignore = 0;

		for (j = 0; address_data->ignore[j] != I2C_CLIENT_END;

		     j += 2) {

			if ((address_data->ignore[j] == adap_id ||

			     address_data->ignore[j] == ANY_I2C_BUS)

			 && address_data->ignore[j + 1]

			    == address_data->normal_i2c[i]) {

				dev_dbg(&adapter->dev, "found ignore "

					"parameter for adapter %d, "

					"addr 0x%02x\n", adap_id,

					address_data->ignore[j + 1]);

			}

			ignore = 1;

			break;

		}

		if (!found) 

		if (ignore)

			continue;



		/* OK, so we really should examine this address. First check

		   whether there is some client here at all! */

		if (i2c_smbus_xfer(adapter,addr,0,0,0,I2C_SMBUS_QUICK,NULL) >= 0)

			if ((err = found_proc(adapter,addr,-1)))

		dev_dbg(&adapter->dev, "found normal entry for adapter %d, "

			"addr 0x%02x\n", adap_id,

			address_data->normal_i2c[i]);

		err = i2c_probe_address(adapter, address_data->normal_i2c[i],

					-1, found_proc);

		if (err)

			return err;

	}



	return 0;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE