[U-Boot] [PATCH v2 26/29] dm: Add child_pre_probe() and child_post_remove() methods

[Simon Glass]

Hi Pavel,

On 17 July 2014 01:09, Pavel Herrmann <morpheus.ibis at gmail.com> wrote:
>
> On Wednesday 16 of July 2014 23:41:57 Simon Glass wrote:
> > Hi Pavel,
> >
> > On 15 July 2014 02:26, Pavel Herrmann <morpheus.ibis at gmail.com> wrote:
> > > Hi
> > >
> > > On Tuesday 08 of July 2014 21:38:16 Simon Glass wrote:
> > >> ...
> > >> +
> > >> +Note that the information that controls this behaviour is in the bus's
> > >> +driver, not the child's. In fact it is possible that child has no
> > >> knowledge +that it is connected to a bus. The same child device may even
> > >> be used on two +different bus types. As an example. the 'flash' device
> > >> shown above may also +be connected on a SATA bus or standalone with no
> > >> bus:
> > >> +
> > >> +   xhci_usb (UCLASS_USB)
> > >> +      flash (UCLASS_FLASH_STORAGE)  - parent data/methods defined by USB
> > >> bus +
> > >> +   sata (UCLASS_SATA)
> > >> +      flash (UCLASS_FLASH_STORAGE)  - parent data/methods defined by
> > >> SATA
> > >> bus +
> > >> +   flash (UCLASS_FLASH_STORAGE)  - no parent data/methods (not on a bus)
> > >
> > > this is not the best example, since the driver actually needs to have an
> > > idea what parent bus it is connected to, as it should use the parents
> > > driver.ops to communicate with the device.
> >
> > Yes, it's not a good example.
> >
> > > the better (more realistic) version would show that the same device would
> > > operate under various xhci_usb, ohci_usb and ehci_usb busses, which might
> > > very well have different parent_priv structure (for example, ohci_usb
> > > would probably not store maximum speed supported by the device, since the
> > > bus only has the basic one)
> >
> > They still use the parent driver ops, but now they are all the same?
> > Do you mean that the uclass would be the same for each bus?
>
> Yes, I imagine the uclass for USB host controller would the same, not
> depending on the speed of the controller.

OK, but there is no requirement for the child data to be the same for
each USB device. Each device has its own child data structure - this
is not defined by the uclass but by the udevice.

Regards,
Simon