Hi Pavel, On 15 July 2014 02:26, Pavel Herrmann <morpheus.i...@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? > > as a side note, flash is a bit tricky here, since USB and SATA do not provide > you with "flash-like" interface even for flash-based devices, but instead > have a > disk-like interface, which is simpler (does not give you the ability to > control bad block management, among other things). Another reason why the example is poor - I was more thinking of flash as a disk than a raw NAND device. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
