Re: i2c: Documentation: upgrading clients HOWTO

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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Hi Ben,

some minor remarks...

On Tue, Jul 15, 2008 at 04:51:44PM +0100, Ben Dooks wrote:
> Add a document describing how i2c clients on Linux 2.6 can be
> moved from the old to the new driver model.
> 
> Signed-off-by: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
> 
> Index: linux-2.6.26-quilt2/Documentation/i2c/upgrading-clients
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.26-quilt2/Documentation/i2c/upgrading-clients	2008-07-15 16:51:11.000000000 +0100
> @@ -0,0 +1,280 @@
> +Upgrading I2C Drivers to the new 2.6 Driver Model
> +=================================================
> +
> +Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
> +
> +Introduction
> +------------
> +
> +This guide outlines how to alter existing Linux 2.6 client drivers from
> +the old to the new new binding methods.
> +
> +
> +Example old-style driver
> +------------------------
> +
> +
> +struct example_state {
> +	struct i2c_client	client;
> +	....
> +};
> +
> +static struct i2c_driver example_driver;
> +
> +static unsigned short ignore[] = { I2C_CLIENT_END };
> +static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
> +
> +I2C_CLIENT_INSMOD;
> +
> +static int example_attach(struct i2c_adapter *adap, int addr, int kind)
> +{
> +	struct example_state *state;
> +	struct device *dev = &adap->dev;  /* to use for dev_ reports */
> +	int ret;
> +
> +	state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
> +	if (state == NULL) {
> +		dev_err(dev, "failed to create our state\n");
> +		return -ENOMEM;
> +	}
> +
> +	example->client.addr    = addr;
> +	example->client.flags   = 0;
> +	example->client.adapter = adap;
> +
> +	i2c_set_clientdata(&state->i2c_client, state);
> +	strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
> +
> +	ret = i2c_attach_client(&state->i2c_client);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to attach client\n");
> +		kfree(state);
> +		return ret;
> +	}
> +
> +	dev = &state->i2c_client.dev;
> +
> +	/* rest of the initialisation goes here. */
> +
> +	dev_info(dev, "example client created\n");
> +
> +	return 0;
> +}
> +
> +static int example_detach(struct i2c_client *client)
> +{
> +	struct example_state *state = i2c_get_clientdata(client);
> +
> +	i2c_detach_client(client);
> +	kfree(state);
> +	return 0;
> +}
> +
> +static int example_attach_adapter(struct i2c_adapter *adap)
> +{
> +	return i2c_probe(adap, &addr_data, example_attach);
> +}
> +
> +static struct i2c_driver example_driver = {
> + 	.driver		= {
> +		.owner		= THIS_MODULE,
> +		.name		= "example",
> +	},
> +	.attach_adapter = example_attach_adapter,
> +	.detach_client	= example_detach,
> +	.suspend	= example_suspend,
> +	.resume		= example_resume,
> +};
> +
> +
> +Updating the client
> +-------------------
> +
> +The new style binding model will check against a list of supported
> +devices and their associated address supplied by the code registering
> +the busses. This means that the driver .attach_adapter and
> +.detach_adapter methods can be removed, along with the addr_data,
> +as follows:
> +
> +- static struct i2c_driver example_driver;
> +
> +- static unsigned short ignore[] = { I2C_CLIENT_END };
> +- static unsigned short normal_addr[] = { OUR_ADDR, I2C_CLIENT_END };
> +
> +- I2C_CLIENT_INSMOD;
> +
> +- static int example_attach_adapter(struct i2c_adapter *adap)
> +- {
> +- 	return i2c_probe(adap, &addr_data, example_attach);
> +- }
> +
> + static struct i2c_driver example_driver = {
> +-	.attach_adapter = example_attach_adapter,
> +-	.detach_client	= example_detach,
> + }
> +
> +Add the probe and remove methods to the i2c_driver, as so:
> +
> + static struct i2c_driver example_driver = {
> ++	.probe		= example_probe,
> ++	.remove		= example_remove,
> + }
> +
> +Change the example_attach method to accept the new parameters
> +which include the i2c_client that it will be working with:
> +
> +- static int example_attach(struct i2c_adapter *adap, int addr, int kind)
> ++ static int example_probe(struct i2c_client *client,
> ++			   const struct i2c_device_id *id)
> +
> +Change the name of example_attach to example_probe to align it with the
> +i2c_driver entry names. The rest of the probe routine will now need to be
> +changed as the i2c_client has already been setup for use.
> +
> +The necessary client fields have already been setup before
> +the probe function is called, so the following client setup
> +can be removed:
> +
> +-	example->client.addr    = addr;
> +-	example->client.flags   = 0;
> +-	example->client.adapter = adap;
> +-
> +-	strlcpy(client->i2c_client.name, "example", I2C_NAME_SIZE);
> +
> +The i2c_set_clientdata is now:
> +
> +-	i2c_set_clientdata(&state->client, state);
> ++	i2c_set_clientdata(client, state);
> +
> +The call to i2c_attach_client is no longer needed, if the probe
> +routine exits successfully, then the driver will be automatically
> +attached by the core. Change the probe routine as so:
> +
> +-	ret = i2c_attach_client(&state->i2c_client);
> +-	if (ret < 0) {
> +-		dev_err(dev, "failed to attach client\n");
> +-		kfree(state);
> +-		return ret;
> +-	}
> +
> +
> +Remove the storage of 'struct i2c_client' from the 'struct example_state'
> +as we are provided with the i2c_client in our example_probe. Instead we
> +store a pointer to it for when it is needed.
> +
> +struct example_state {
> +-	struct i2c_client	client;
> ++	struct i2c_client	*client;
> +
> +the new i2c client as so:
> +
> +-	struct device *dev = &adap->dev;  /* to use for dev_ reports */
> ++ 	struct device *dev = &i2c_client->dev;  /* to use for dev_ reports */
> +
> +And remove the change after our client is attached, as the driver no
> +longer needs to register a new client structure with the core:
> +
> +-	dev = &state->i2c_client.dev;
> +
> +In the probe routine, ensure that the new state has the client stored
> +in it:
> +
> +static int example_probe(struct i2c_client *i2c_client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct example_state *state;
> + 	struct device *dev = &i2c_client->dev;
> +	int ret;
> +
> +	state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
> +	if (state == NULL) {
> +		dev_err(dev, "failed to create our state\n");
> +		return -ENOMEM;
> +	}
> +
> ++	state->client = i2c_client;
> +
> +Update the detatch method, by changing the name to _remove and
Typo: detach

> +to delete the i2c_detach_client call.
> +
> +- static int example_detach(struct i2c_client *client)
> ++ static int example_remove(struct i2c_client *client)
> +{
> +	struct example_state *state = i2c_get_clientdata(client);
> +
> +-	i2c_detach_client(client);
> +
> +And finally ensure that we have the correct ID table for the i2c-core
> +and other utilties:
Typo: utilities

> +
> ++ struct i2c_device_id example_idtable[] = {
> ++       { "example", 0 },
> ++       { }
> ++};
> ++
> ++MODULE_DEVICE_TABLE(i2c, example_idtable);
> +
> +static struct i2c_driver example_driver = {
> + 	.driver		= {
> +		.owner		= THIS_MODULE,
> +		.name		= "example",
> +	},
> ++	.id_table	= example_ids,
> +
> +
> +Our driver should now look like this:
> +
> +struct example_state {
> +	struct i2c_client	*client;
> +	....
> +};
> +
> +static int example_probe(struct i2c_client *client,
> +		         const struct i2c_device_id *id)
> +{
> +	struct example_state *state;
> +	struct device *dev = &client->dev;
> +	int ret;
ret is not needed in the updated example. Maybe mention that it could
also be removed?

> +
> +	state = kzalloc(sizeof(struct example_state), GFP_KERNEL);
> +	if (state == NULL) {
> +		dev_err(dev, "failed to create our state\n");
> +		return -ENOMEM;
> +	}
> +
> +	state->client = client;
> +	i2c_set_clientdata(client, state);
> +
> +	/* rest of the initialisation goes here. */
> +
> +	dev_info(dev, "example client created\n");
> +
> +	return 0;
> +}
> +
> +static int example_remove(struct i2c_client *client)
__devexit

> +{
> +	struct example_state *state = i2c_get_clientdata(client);
> +
> +	kfree(state);
> +	return 0;
> +}
> +
> +static struct i2c_device_id example_idtable[] = {
> +	{ "example", 0 },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, example_idtable);
> +
> +static struct i2c_driver example_driver = {
> + 	.driver		= {
> +		.owner		= THIS_MODULE,
> +		.name		= "example",
> +	},
> +	.id_table	= example_idtable,
> +	.probe		= example_probe,
> +	.remove		= example_remove,
__devexit_p

> +	.suspend	= example_suspend,
> +	.resume		= example_resume,
> +};
> 
> -- 
> Ben (ben-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, http://www.fluff.org/)
> 
>   'a smiley only costs 4 bytes'
> 
> _______________________________________________
> i2c mailing list
> i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org
> http://lists.lm-sensors.org/mailman/listinfo/i2c

Thanks for this work!

All the best,

   Wolfram

-- 
  Dipl.-Ing. Wolfram Sang | http://www.pengutronix.de
 Pengutronix - Linux Solutions for Science and Industry

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