Hi Ben,
On Tue, 3 Jun 2008 14:46:37 +0100, Ben Dooks wrote:
> On Tue, Jun 03, 2008 at 01:29:06PM +0200, Laurent Pinchart wrote:
>
> Thanks, here's the next version, and I have included the example
> driver post-editing at the end of the file. Also found a couple of
> items that I forgot to add.
>
> V2:
>
> Upgrading I2C Drivers to the new 2.6 Driver Model
> =================================================
That's a good idea, thanks for doing this.
>
> Ben Dooks <[EMAIL PROTECTED]>
>
> 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 };
>
> static struct i2c_client_address_data addr_data = {
> .normal_i2c = normal_addr,
> .probe = ignore,
> .ignore = ignore,
> };
You could make the example slightly shorter with:
I2C_CLIENT_INSMOD;
>
> static int example_attach(struct i2c_adapter *adap, int addr, int kind)
> {
> struct example_state *state;
> struct device *dev = &adap->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;
> }
>
> example->i2c_client.addr = addr;
example->client.addr, same below and again later in the document.
> example->i2c_client.flags = 0;
> example->i2c_client.adapter = adap;
>
> i2c_set_clientdata(&state->i2c_client, state);
> strlcpy(client->i2c_client.name, example_driver.driver.name,
It's a bad example, driver name != client name. Just use "example" as
the client name. Would save you a forward declaration as well.
> 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;
Doesn't seem terribly useful given that you skip all the code that
would use it.
>
> /* rest of the initialisation goes here. */
>
> return 0;
> }
>
> static int example_remove(struct i2c_client *client)
example_detach
> {
> 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 };
>
> - static struct i2c_client_address_data addr_data = {
> - .normal_i2c = normal_addr,
> - .probe = ignore,
> - .ignore = ignore,
> - };
>
> - 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 *i2c_client,
The client is typically named client, not i2c_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.
>
> Remove the setting of address and adapter, they are now not needed.
>
> - example->i2c_client.addr = addr;
> - example->i2c_client.flags = 0;
> - example->i2c_client.adapter = adap;
>
> Also remove the strlcpy, as the i2c_client's name is already filled
> in by the caller.
>
> - strlcpy(client->i2c_client.name, example_driver.driver.name,
> - I2C_NAME_SIZE);
In fact, the 3 items before are in the exact same case: they have
already been set by the caller.
>
> The i2c_set_clientdata is now:
>
> - i2c_set_clientdata(&state->i2c_client, state);
> + i2c_set_clientdata(i2c_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;
> - }
>
>
Doubled blank line.
> Remove the storage of 'struct i2c_client' from the 'struct example_state'
Doubled space.
> 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;
>
> It is also necessary to change the temporary dev pointer to point into
> the new i2c client as so:
>
> - struct device *dev = &adap->dev;
> + struct device *dev = &i2c_client->dev;
This is an implementation detail, many drivers don't use a local
pointer for that, and it's IMHO rather confusing to present this as if
an adapter had turned into a client. I think you can simply omit this,
it's not worth insisting on.
>
> And remove the change aftre our client is attached, as the driver no
Typo: after.
> 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 remove method to delete the i2c_detach_client call.
>
> static int example_remove(struct i2c_client *client)
> {
> struct example_state *state = i2c_get_clientdata(client);
>
> - i2c_detach_client(client);
>
>
>
> Our driver should now look like this:
>
> struct example_state {
> struct i2c_client client;
*client
> ....
> };
>
> static int example_probe(struct i2c_client *i2c_client,
*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;
> i2c_set_clientdata(i2c_client, state);
>
> /* rest of the initialisation goes here. */
>
> return 0;
> }
>
> static int example_remove(struct i2c_client *client)
> {
> struct example_state *state = i2c_get_clientdata(client);
>
> kfree(state);
> return 0;
> }
>
> static struct i2c_driver example_driver = {
> .driver = {
> .owner = THIS_MODULE,
> .name = "example",
> },
> .probe = example_probe,
> .remove = example_remove,
> .suspend = example_suspend,
> .resume = example_resume,
> };
--
Jean Delvare
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