[PATCH 03/16] arm: stm32mp: reset to default environment when serial# change

[Patrick DELAUNAY]

Dear Wolfgang,

> From: Wolfgang Denk <wd at denx.de>
> Sent: mercredi 1 avril 2020 13:19
> 
> Dear Patrick,
> 
> In message
> <20200331180330.3.I8f6df6d28ce5b4b601ced711af3699d95e1576fb at changeid>
> you wrote:
> > Serial number is first checked and, in case of mismatch, all
> > environment variables are reset to their default value.
> >
> > This patch allows to detect that environment is saved in a removable
> > device, as a SD card, and reused on a other board, potentially with
> > incompatible variables.
> >
> > Signed-off-by: Patrick Delaunay <patrick.delaunay at st.com>
> > ---
> >
> >  arch/arm/mach-stm32mp/cpu.c | 20 +++++++++++++++-----
> >  1 file changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/arm/mach-stm32mp/cpu.c b/arch/arm/mach-stm32mp/cpu.c
> > index 9aa5794334..365c2aa4f7 100644
> > --- a/arch/arm/mach-stm32mp/cpu.c
> > +++ b/arch/arm/mach-stm32mp/cpu.c
> > @@ -511,8 +511,9 @@ __weak int setup_mac_address(void)
> >  		return -EINVAL;
> >  	}
> >  	pr_debug("OTP MAC address = %pM\n", enetaddr);
> > -	ret = !eth_env_set_enetaddr("ethaddr", enetaddr);
> > -	if (!ret)
> > +
> > +	ret = eth_env_set_enetaddr("ethaddr", enetaddr);
> > +	if (ret)
> >  		pr_err("Failed to set mac address %pM from OTP: %d\n",
> >  		       enetaddr, ret);
> 
> This is an unrelated and totally undocumented change.  Please split into separate
> commit.

Yes, sorry.

Done in http://patchwork.ozlabs.org/project/uboot/list/?series=169021
" arm: stm32mp: cleanup test on eth_env_set_enetaddr result"

> 
> > +
> > +	if (serial_env) {
> > +		if (!strcmp(serial_string, serial_env))
> > +			return 0;
> > +		/* For invalid enviromnent (serial# change), reset to default */
> > +		env_set_default("serial number mismatch", 0);
> > +	}
> 
> Resetting the enviropnment to the defaults means you drop all setting sa user
> may have made.  This is a very bad move - as a user I find such things
> completely unacceptable.  If I make any changes, they must never ever be killed
> without my explicit confirmation.
> 
> I strongly advice against such a method. Please drop that.

Understood, I drops this patch....

I introduce this behavior after a internal request and to avoid issues during tests:

Some users use the same SD card (same rootfs) on several boards (EV1 and DK2 for example)
and the U-Boot environment is saved on this SD card. 

When an user updates U-Boot binary to use this SD card on other board but not erase the
environment file (save in ext4 file in bootfs partition), the boot can fail because the
environment is not compatible between the 2 boards.

This patch try to avoid this issue when I detect that the removable device (as SD card) is used on a
a different board (it is detected when saved serial number with different the OTP).

But I admit that can be strange/unacceptable for end-user, particularly it is only change of board
(DK2#1 => DK2#2) : the environment tuned one board #2 can't be used on board#2.

I make too many assumption on user usage and this patch can't be acceptable in arch 
(common for all board based on STM32MP15x).
 
> Best regards,
> 
> Wolfgang Denk
> 
> --
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de "You
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