Re: [PATCH v3] add analog devices AD714X captouchinput driver

[Mike Frysinger <vapier.adi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Fri, Sep 11, 2009 at 09:19, Hennerich, Michael wrote:
> On Friday 11 September 2009, Song, Barry wrote:
> +static int __init ad714x_init(void)
> +{
> +
> +       int ret = 0;
> +       ret = ad714x_spi_register_driver(&ad714x_spi_driver);
> +       if (ret)
> +               goto err;
> +       ret = ad714x_i2c_add_driver(&ad714x_i2c_driver);
> +       if (ret)
> +               ad714x_spi_unregister_driver(&ad714x_spi_driver);
> +err:
> +       return ret;
> +}
> +
> +static void __exit ad714x_exit(void)
> +{
> +       ad714x_spi_unregister_driver(&ad714x_spi_driver);
> +       ad714x_i2c_del_driver(&ad714x_i2c_driver);
> +}
>
> This doesn't make much sense!
> Assuming we have two AD714x in a system. One connected by SPI the other
> by I2C.
> Why would I remove the SPI one in case the other I2C fails, or not even
> try the SPI one if the I2C fails?

is this a realistic problem ?  we arent talking about failure to probe
the device, we're talking about failure to register the driver as
available.  i.e. the only way the module_init step should fail is if
i2c_add_driver() or spi_register_driver() fails.  and if either of
those fail, it's most likely a pretty bad situation.

failure to probe/detect/talk to the device are a different issue and a
problem with one interface will not affect the other.

> Who says that a driver can't have two module_init()?

Mr. C Code says it wont work.  if ad714x is built as a module and both
I2C and SPI support are enabled, we get:
drivers/input/misc/ad714x.c:1621: error: redefinition of ‘__inittest’
drivers/input/misc/ad714x.c:1492: error: previous definition of
‘__inittest’ was here

these lines correspond to the module_init() macro

linux/init.h says:
/* Each module must use one module_init(). */
#define module_init(initfn)                 \
    static inline initcall_t __inittest(void)       \
    { return initfn; }                  \
    int init_module(void) __attribute__((alias(#initfn)));

and indeed, the error makes sense -- you cant have multiple functions
named the same thing (in this case, we'd have two __inittest() and two
init_module())
-mike
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