[U-Boot] [U-Boot, resend, 1/2] config_distro_bootcmd.h: Allow user to indicate that usb is inited in preboot

[Hans de Goede <hdegoede@redhat.com>]

On 12/12/2014 Stephen Warren wrote:

 > On 12-12-14 10:50 AM, Hans de Goede wrote:
> > When using usb-keyboard support, typically usb will already get started from
> > preboot. In this case doing it again in the bootcmd is undesirable.
> >
> > Allow the user of config_distro_bootcmd to indicate that usb is inited in
> > preboot through the user setting BOOTENV_PREBOOT_INITS_USB.
>
>Sorry, I don't recall seeing this whenever it was posted before.
 >
 > Conceptually this seems fine. One issue it has is with the following
 > sequence:
 >
 > PREBOOT inits USB, no USB drive found (not plugged in)
 > User CTRL-Cs boot sequence
 > User plugs in USB drive
 > User runs "boot" or "run bootcmd"
 > -> USB not re-detected, so system doesn't boot from USB.
 >
 > Perhaps the best way to solve this is to have a flag controlling whether
 > BOOTENV_SET_USB_NEED_INIT sets $usb_need_init?
 >
 > preboot:
 > setenv usb_do_set_usb_need_init false
 >
 > BOOTENV_SET_USB_NEED_INIT:
 > # Normally unset -> true
 > # In your case, preboot sets this to false
 > if ${usb_do_set_usb_need_init}; then
 >      setenv usb_need_init
 > else
 >      # Next time $boot is run, this will be unset -> true
 >      # so we will re-init USB
 >      setenv usb_do_set_usb_need_init
 >      # This time through, we skip USB init
 >      setenv usb_need_init false
 > endif
 >
 > Of course, that doesn't solve the problem of the user aborting auto-boot
 > before it's ever run once. Perhaps better would be a flag that
 > BOOTENV_SET_USB_NEED_INIT can use to distinguish auto-boot and manual
 > invocation, i.e.:
 >
 > preboot:
 > setenv usb_do_set_usb_need_init false
 >
 > BOOTENV_SET_USB_NEED_INIT:
 > # U-Boot C code sets this appropriatelyL
 > if ${auto_boot}; then
 >      # Auto case: Init USB unless preboot set a flag
 >      if ${usb_do_set_usb_need_init}; then
 >          setenv usb_need_init
 >      else
 >          # Next time $boot is run, this will be unset -> true
 >          # so we will re-init USB
 >          setenv usb_do_set_usb_need_init
 >          # This time through, we skip USB init
 >          setenv usb_need_init false
 >      endif
 > else
 >      # Manual case: Always init USB
 >      setenv usb_need_init
 > endif
 >
 > Or do we just assume that if the user plugs in a new USB device after
 > boot, they must manually run USB initialization? If so, we cam simplify
 > the existing $usb_need_init a bit...

Looking at all the extra code (and possible bugs / problems that code may
introduce), I think that it makes sense to just expect the user to run
"usb reset" after plugging in a new device.

Regards,

Hans