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

[Maxime Ripard <maxime.ripard@free-electrons.com>]

On Sun, Mar 12, 2017 at 02:21:35PM -0600, Simon Glass wrote:
> Hi,
> 
> On 3 March 2017 at 03:52, Dr. Philipp Tomsich
> <philipp.tomsich@theobroma-systems.com> wrote:
> > Hi Simon,
> >
> > On 03 Mar 2017, at 05:52, Simon Glass <sjg@chromium.org> wrote:
> >
> > Hi Philipp,
> >
> > On 22 February 2017 at 13:47, Philipp Tomsich
> > <philipp.tomsich@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.

It does, but it's not really what we're doing in the linux driver. It
has one driver, with one device, but registering into multiple
frameworks.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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