Re: [PATCH v5 1/8] i2c: core: let adapters be notified of client attach/detach

Laurent Pinchart
2022-12-26T16:55:18Z

On Mon, Dec 19, 2022 at 11:48:51AM +0200, Andy Shevchenko wrote:
> On Mon, Dec 19, 2022 at 09:51:43AM +0100, Luca Ceresoli wrote:
> > On Sun, 11 Dec 2022 18:55:39 +0200 Laurent Pinchart wrote:
> > > On Thu, Dec 08, 2022 at 12:39:59PM +0200, Tomi Valkeinen wrote:
>
> ...
>
> > > This may be a stupid question, but couldn't you instead use the
> > > BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers ?
> >
> > I'm not sure they would be the correct tool for this task. Bus
> > notifiers inform about new events on the 'struct bus_type, i.e. any
> > event on the global i2c bus type. In the i2c world this means being
> > notified about new _adapters_, which is exactly what
> > drivers/i2c/i2c-dev.c does.
> >
> > Here, however, we need to be informed about new _clients_ being added
> > under a specific adapter.
>
> This is for example exactly what ACPI integration in I2C framework does. But...
>
> > I'm not sure whether the bus notifiers can
> > inform about new clients in addition of new adapters, but they at least
> > seem unable to provide per-adapter notification.
>
> ...personally I don't like notifiers, they looks like overkill for this task.

But isn't this patch essentially implementing a custom notification
system ? If we need notifiers, why would it be better to add an ad-hoc
API for I2C instead of using bus notifiers ?

> > Does that seem correct?

--
Regards,

Laurent Pinchart