Re: [PATCH v4 05/15] drivers: platform: add fwnode base platform devices retrieval

[Hanjun Guo]

On 2016/9/5 22:57, Lorenzo Pieralisi wrote:
> On Mon, Sep 05, 2016 at 09:19:43PM +0800, Hanjun Guo wrote:
> > On 2016/8/15 23:23, Lorenzo Pieralisi wrote:
> > > The platform device kernel API does not provide functions to
> > > retrieve a platform device through the corresponding struct
> > > device fwnode pointer.
> > >
> > > Implement the fwnode platform_device look-up in drivers core
> > > code by using the bus_find_device() API and a corresponding
> > > matching function. The OF equivalent (eg of_find_device_by_node())
> > > will reuse the newly introduced function when OF code will
> > > take care of setting up the device->fwnode value that is
> > > currently left dangling for platform devices instantiated out
> > > of device tree nodes.
> > >
> > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> > > ---
> > > drivers/base/platform.c         | 23 +++++++++++++++++++++++
> > > include/linux/platform_device.h |  3 +++
> > > 2 files changed, 26 insertions(+)
> > >
> > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > > index 6482d47..3ef150d 100644
> > > --- a/drivers/base/platform.c
> > > +++ b/drivers/base/platform.c
> > > @@ -760,6 +760,29 @@ err_out:
> > > }
> > > EXPORT_SYMBOL_GPL(__platform_create_bundle);
> > >
> > > +static int fwnode_dev_match(struct device *dev, void *data)
> > > +{
> > > +	return dev->fwnode == data;
> > > +}
> > > +
> > > +/**
> > > + * platform_find_device_by_fwnode() - Find the platform_device associated
> > > + *				      with a fwnode
> > > + * @fwnode: Pointer to firmware node
> > > + *
> > > + * Returns platform_device pointer, or NULL if not found
> > > + */
> > > +struct platform_device *
> > > +platform_find_device_by_fwnode(struct fwnode_handle *fwnode)
> > > +{
> > > +	struct device *dev;
> > > +
> > > +	dev = bus_find_device(&platform_bus_type, NULL, fwnode,
> > > +			      fwnode_dev_match);
> > > +	return dev ? to_platform_device(dev) : NULL;
> > > +}
> > > +EXPORT_SYMBOL(platform_find_device_by_fwnode);
> >
> > As SMMU is registered as platform devices, I think we need such
> > API to retrieve the platform device with fwnode handle, actually
> > Kefeng introduced a similar patch [1], but your patch is more
> > generic, so this patch make sense to me,
> >
> > Reviewed-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>
> Thanks ! Strictly speaking, with Robin's new series:
>
> https://lists.linuxfoundation.org/pipermail/iommu/2016-August/018230.html
>
>
> (and corresponding v5 of this one that I have rebased on top of it) we
> do not need this patch any longer and it is not really that generic
> keeping in mind that it can't be used for DT matching (because in DT
> dev->fwnode is dangling); I will see if I keep this patch according
> to dependencies.

OK, I think I will wait for your new version, then try another test
and review it, does it make sense?

> Side note: I have a problem with [1], since that code is there to
> implement DT phandles in ACPI IIUC and we must really prevent that :)

Agreed :)

Thanks
Hanjun