[PATCH v2 00/41] Initial implementation of standard boot

[Tom Rini]

On Thu, Oct 28, 2021 at 06:50:02PM +0100, Peter Robinson wrote:
> On Thu, Oct 28, 2021 at 6:47 PM Tom Rini <trini at konsulko.com> wrote:
> >
> > On Thu, Oct 28, 2021 at 06:37:42PM +0100, Peter Robinson wrote:
> > > On Wed, Oct 27, 2021 at 3:11 PM Simon Glass <sjg at chromium.org> wrote:
> > > >
> > > > Hi Heinrich,
> > > >
> > > > On Wed, 27 Oct 2021 at 05:38, Heinrich Schuchardt
> > > > <heinrich.schuchardt at canonical.com> wrote:
> > > > >
> > > > >
> > > > >
> > > > > On 10/24/21 01:25, Simon Glass wrote:
> > > > > >
> > > > > > The bootflow feature provide a built-in way for U-Boot to automatically
> > > > > > boot an Operating System without custom scripting and other customisation.
> > > > > > This is called 'standard boot' since it provides a standard way for
> > > > > > U-Boot to boot a distro, without scripting.
> > > > > >
> > > > > > It introduces the following concepts:
> > > > > >
> > > > > >     - bootdev - a device which can hold a distro
> > > > > >     - bootmeth - a method to scan a bootdev to find bootflows (owned by
> > > > > >                  U-Boot)
> > > > > >     - bootflow - a description of how to boot (owned by the distro)
> > > > >
> > > > > Please, describe why you are suggesting this change.
> > > > >
> > > > > Replacing a script by a devicetree chunk is just decreasing flexibility
> > > > > and increasing complexity. Where is the benefit?
> > > > >
> > > > > I am missing a description here of where and how a boot flow shall be
> > > > > defined. Describing some device-tree binding in patch 40/41 does not
> > > > > replace describing the development and usage workflow. Who will provide
> > > > > which bootflow information when?
> > > > >
> > > > > You still have an open discussion with Linaro about the source of
> > > > > devicetrees. This discussion needs to be finalized before considering
> > > > > this series.
> > > > >
> > > > > In my view bootflows cannot be defined in the devicetree because prior
> > > > > firmware providing a devicetree is completely independent of any distro
> > > > > and therefore cannot provide a distro specific bootflow.
> > > >
> > > > There is actually no need to use devicetree here. I think you might
> > > > have the wrong end of the stick. It is certainly possible to add nodes
> > > > to configure things, if needed, but it works find without any changes
> > > > to the devicetree, as you can see from the rpi_3 patch.
> > > >
> > > > There are several aims with this effort:
> > > >
> > > > - Provide a standard way to boot anything on U-Boot, that everyone can
> > > > plug into (distros, board vendors, people using a custom flow)
> > >
> > > I as a distro maintainer don't want this, we already get the "standard
> > > way to boot" from UEFI, this just feels like another unnecessary
> > > abstraction to that.
> >
> > Right.  But part of the problem is "How do I find UEFI".  Something
> > somewhere needs to be configurable to say where to look, yes?
> 
> Is this question from the board PoV, the developer of U-Boot or the
> distro trying to boot?
> 
> If you mean from a boot flow PoV for UEFI to find the HW that contains
> the OS to boot I thought that was handled elsewhere in the series.

What I mean is that today looking at Pi we have:
#define BOOT_TARGET_DEVICES(func) \
        BOOT_TARGET_MMC(func) \
        BOOT_TARGET_USB(func) \
        BOOT_TARGET_PXE(func) \
        BOOT_TARGET_DHCP(func)

As the board maintainer set that as the list of places to start looking
for the next payload (say the GRUB EFI binary).  Simon's series replaces
that with I think he said "bootflow scan -b".  And then the above env
portion is replaced with, well, what's documented in patch #40 if you
don't just want to rely on device probe order.

Because we need to have _something_ that says where to look for what,
yes?  Or should that be replaced entirely with efi vars and
BootOrder/BootXXX and "bootefi bootmgr $fdt_addr_r" ?

-- 
Tom
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