[PATCH 00/17] arm: semihosting: Cleanups and new features

[Sean Anderson]

Hi Andre,

On 3/4/22 6:47 AM, Andre Przywara wrote:
> On Fri, 4 Mar 2022 02:06:03 +0100
> Linus Walleij <linus.walleij at linaro.org> wrote:
> 
> Hi,
> 
> Linus, thanks for the heads up, much appreciated!
> 
>> On Thu, Mar 3, 2022 at 9:44 PM Sean Anderson <sean.anderson at seco.com> wrote:
>> 
>> > The main device affected by these changes is vexpress64, so I'd appreciate
>> > if Linus (or anyone else) could try booting.  
> 
> As it happens, I am sitting on a series updating vexpress_aemv8a_semi, and
> letting it use OF_CONTROL. I will send this ASAP.
> As it turned out, the automatic semihosting boot command is actually broken
> in v2022.01, the fix is the first patch in my series. This clashes with
> this series, but it's easy to resolve.

I, for one, appreciate that the boot command is no longer all one line after
your series.

Simon/Tom, which series would you like to be based off the other?

> From skimming over this series here, it looks quite nice, I especially love
> promoting the semihosting load to a proper filesystem. The only drawback
> seems to be that this will break existing scripts used by people in their
> deployments, which rely on the smhload command. I don't really know if
> there are actually any users doing so, but I guess we will find out.

Yeah, I'm not sure what the stance on shell compatibility is. As I understand
it, for the C API only in-tree users matter. However, shell commands are more
of an "external" API, used by distro boot scripts. Simon/Tom, what's the
process for this?

There are two ABI breaks introduced by this series:
- Changing smh_load to set the size and not the end address
- Removing the smh_load command altogether

The first one could be avoided by loading a FIT instead of individual images
(since we would no longer need to fix up chosen to point at the ramdisk). The
second could be avoided by providing a small shim like do_ext4_load. However,
if at all possible I would just like to remove the command entirely.

> Is there any official U-Boot policy for changing commands, which might
> break scripts? For instance I was always tempted to fix the "afs" command,
> or make that an fs as well.
> 
> I will test and review this series ASAP.

Thanks. BTW what does U-Boot use for its console on this platform? From the
bootargs, it appears that Linux uses pl011, but that doesn't seem to be
enabled for U-Boot.

>> I am currently on parental leave and pretty far removed from that hardware
>> and have very little bandwidth. I added Andre Przywara to the header
>> (include him in the future) because currently he does much more U-Boot
>> work on these platforms than me.

Thanks for pointing me to the right person.

--Sean