[U-Boot] [PATCH v2 2/6] dm: core: Allow multiple drivers to bind for a single node

[Simon Glass]

Hi,

On 3 March 2017 at 03:52, Dr. Philipp Tomsich
<philipp.tomsich at theobroma-systems.com> wrote:
> Hi Simon,
>
> On 03 Mar 2017, at 05:52, Simon Glass <sjg at chromium.org> wrote:
>
> Hi Philipp,
>
> On 22 February 2017 at 13:47, Philipp Tomsich
> <philipp.tomsich at theobroma-systems.com> wrote:
>
> Currently, driver binding stops once it encounters the first
> compatible driver that doesn't refuse to bind. However, there are
> cases where a single node will need to be handled by multiple driver
> classes. For those cases we provide a configurable option to continue
> to bind after the first driver has been found.
>
> The first use cases for this are from the DM conversion of the sunxi
> (Allwinner) architecture:
> * pinctrl (UCLASS_PINCTRL) and gpio (UCLASS_GPIO) drivers need to
>   bind against a single node
> * clock (UCLASS_CLK) and reset (UCLASS_RESET) drivers also need to
>   bind against a single node
>
>
> Does linux work this way? Another approach would be to have a separate
> MISC driver with two children, one pinctrl, one clk.
>
>
> The linux CLK driver creates and registers a reset-controller; the PINCTRL
> driver
> does the same with the gpio-controller. Similar code to do this is easily
> possible in
> U-Boot … see sunxi_pctrl_bind_gpio(…) in [PATCH v2 1/6] of this series.
>
> However, binding multiple times makes for much simpler code and allows to
> keep
> driver data in separate drivers.

My question was more whether Linux registers multiple drivers with one
device node. It's just not something I expected.

I'm not really convinced on this. It will break the current one-to-one
relationship, and functions like device_get_child_by_of_offset(). I
think it would be better to have a MISC driver with two children.

Regards,
Simon