[U-Boot] [RFC][DFU] Unification of dfu_alt_info alt settings description + command execution

[Tormod Volden <lists.tormod@gmail.com>]

On Wed, Jul 17, 2013 at 4:34 PM, Lukasz Majewski wrote:
> _As a side note:_
>
> I'm now developing proof-of-concept idea of executing set of commands
> sent to u-boot by dfu-util [***].
>
> Rationale for this is the lack of ability to reset u-boot after sending
> data to u-boot via DFU. dfu-util has -R option, but this seems to reset
> usb interface, not the target device.

Actually, dfu-util -R  sends a DFU_DETACH request before performing
the USB reset. The reason for this was long unclear to me, until I
looked at the uboot dfu code (inherited from openmoko):

http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/usb/gadget/f_dfu.c;h=d7ae0c0c6a9f6a95ca3a702d92636eb25e21253c;hb=HEAD#l314

"Proprietary extension: 'detach' from idle mode and get back to
runtime mode in case of USB Reset. As much as I dislike this, we just
can't use every USB bus reset to switch back to runtime mode, since at
least the Linux USB stack likes to send a number of resets in a row :(
"

The hack/abuse of sending a DFU_DETACH when in DFU mode is not part of
the DFU standard, but dfu-util supports it since openmoko was for long
the major target for dfu-util.

If you don't need to switch back from DFU mode to runtime mode, maybe
you can use this to reset u-boot?

Regards,
Tormod