Re: [PATCH 4/6] bus: add driver for the Technologic Systems NBUS

[Linus Walleij]

On Wed, Feb 1, 2017 at 8:56 PM, Sebastien Bourdelin
<sebastien.bourdelin@xxxxxxxxxxxxxxxxxxxx> wrote:
> On 12/30/2016 02:58 AM, Linus Walleij wrote:

>>> +static struct ts_nbus *ts_nbus;
>>
>> Nopes. No singletons please.
>>
>> Use the state container pattern:
>> Documentation/driver-model/design-patterns.txt
>
> I understand the idea but have problem to find a good way to implement it.
>
> Other drivers using the NBUS which are child nodes in the device tree
> will use the ts_nbus_write() and ts_nbus_read() functions, it means these
> drivers should have a pointer to the allocated ts_nbus and pass it to
> the write() and read() functions as an argument if i'm not using a
> singleton here.
> But i'm lacking knowledge on how to properly share this pointer when
> initializing the NBUS driver with the child nodes.

Your child nodes I guess will be instatiated as devices as well.

These devices will have the NBUS driver as .parent in their
struct device I guess. Else the design of this bus is tilted.

If the NBUS driver use dev_set_drvdata(dev, state_container_cookie)
the children can use dev_get_drvdata(dev->parent); to get a pointer to
the same cookie.

The subdrivers don't even need to know the members of the state
container as long as you're just passing a pointer to it. It's
enough if you forward-declare it as a "pointer to some struct":

struct foo;

{
   struct foo *fooptr = dev_get_drvdata(dev->parent);
   write(fooptr, 0x10);

etc

Yours,
Linus Walleij