Re: [sodaville] [PATCH] i2c/i2c-dev: use dynamic minor allocation

[Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>]

* Jean Delvare | 2010-11-25 22:52:46 [+0100]:

>Hi Sebastian,
Hi Jean,

>> > But my main question is: why do you want a unique (or you probably
>> > meant predictable - adapter numbers are already unique by design)
>> > adapter number in the first place? Other systems apparently are doing
>> > just fine without this.
>>
>> Both. I use this number for the device id. This one has to remain unique
>> or sysfs goes crazy.
>
>Which "device id" are you talking about, please? Of course sysfs
The pci driver [0] has in add_i2c_device() the following construct:

     pdev->id = dev->devfn << 3 | bar;

I'm talking about this device id. Here I have to remain unique and here I
though using the pci id would be a good idea. There should be no other
device using "pxa2xx-i2c" as the device name so I should be safe here.

>doesn't accept duplicate entries, but as I said already, uniqueness is

>Precisions, please. "Match my board description" is awfully vague.
>Don't hesitate to be technical, I'm sure I can understand you ;)
Sorry didn't meant to. As you probably know, by "board description" I
meant struct i2c_board_info & i2c_register_board_info(). This is now
covered by of_i2c_register_devices(&i2c->adap)

>> > Also, what if another i2c adapter driver comes up with its own idea of how
>> > adapters should be numbered, and its numbering scheme collides with
>> > your driver?
>>
>> Too bad. I though that I will be on the safe side using using the PCI
>> slot+device number.
>
>This can't be safe until all devices in the world are PCI devices and
>all i2c drivers agree to stick to this rule (i.e. it is enforced by
>i2c-core.) This isn't going to happen anytime soon, I'm afraid.
Now I see what you mean.

>> > Fixed i2c adapter numbers are already supported, but it's up to the
>> > platform initialization code to define them, not the i2c adapter driver.
>>
>> I don't want platform init code.
>
>Why? This is what (almost) everybody does when predictable i2c adapter
>numbers are needed. And you said you have platform data, so presumably
>you already have some form of platform init code (even if it's generic
>code with a custom device tree.)

This sounds good. So I get "pdev->id" from the device tree which should
solve my trouble I have so far.
Thank you.

[0] http://article.gmane.org/gmane.linux.drivers.i2c/7260

Sebastian