Re: [PATCH v2 06/15] ARM: i.MX: scratch: add FDT support

[Marco Felsch <m.felsch@pengutronix.de>]

On 26-02-09, Ahmad Fatoum wrote:
> Hi,
> 
> On 2/9/26 9:50 PM, Marco Felsch wrote:
> > On 26-02-06, Ahmad Fatoum wrote:
> >> How about:
> >>
> >> struct imx_scratch_space {
> >>         union {
> >>                 u8 __b[CONFIG_SCRATCH_SIZE];
> >>                 struct {
> >>                         u32 bootrom_log[128];
> >>                         u32 reserved[128];
> >>                         struct optee_header optee_hdr;
> >>                         u8 fdt[] __aligned(8);
> > 
> > This would require, that the 'fdt' element is always the last element.
> > We could add a comment, but it's rather fragile IMHO.
> 
> What's fragile about it? Next one after you, will not be able to add a
> new member and that's a good thing. They should rework this instead of
> piling extra CONFIG variables with board-specific offsets.

I can live with that if that is fine for you.

> >>                 };
> >>         };
> >> };
> >> static_assert(sizeof(struct imx_scratch_space)
> >>           - offsetof(struct imx_scratch_space, fdt)
> >> 			<= PBL_OPTEE_DTB_MAX_SIZE);
> > 
> > This would introduce a very strict dependency for CONFIG_SCRATCH_SIZE to
> > the not always visible PBL_OPTEE_DTB_MAX_SIZE. As you said:
> 
> Wrap the assert in an #ifdef then.

Sure, but still it would bind the SCARTCH_SIZE very tightly to
PBL_OPTEE_DTB_MAX_SIZE. E.g. this assert would always be triggered if
$someone wants to have a PBL_OPTEE_DTB_MAX_SIZE size of 4K and keep the
default SCRATCH_SIZE of 32K. IMHO this is an surprising behaviour.

However, it's fine for me too, I just wanted to point this out.

> >>>> In that case, this should go to security/Kconfig and be named something
> >>>> like PBL_OPTEE_DTB_MAX_SIZE. There's no need to ask every user that
> >>>> configures barebox about this.
> > 
> > Therefore I would like to use your name suggestion
> > PBL_OPTEE_DTB_MAX_SIZE but keep it loose like RK does.
> > 
> >> The benefits I see:
> >>   - Just one argument to tune (CONFIG_SCRATCH_SIZE) like we already use
> >>     for Rockchip
> > 
> > Rockchip is using two Kconfig switch too (ARCH_ROCKCHIP_ATF_FDT_SIZE).
> 
> Oh, I see. I can send patches to switch this over to
> PBL_OPTEE_DTB_MAX_SIZE then.

Thanks :)

Regards,
  Marco

> 
> > 
> >>   - We still have a dedicated option that can be kept in-sync with the
> >>     exact option value in OP-TEE to find problems at compile-time
> >>   - Only those who actually use OP-TEE will be asked about
> >>     PBL_OPTEE_DTB_MAX_SIZE
> > 
> > Good points!
> > 
> >> Would this work for you?
> > 
> > Please see above.
> 
> Cheers,
> Ahmad
> 
> > 
> > Regards,
> >   Marco
> > 
> > 
> >>
> >> Cheers,
> >> Ahmad
> >>
> >>
> >>>
> >>> Regards,
> >>>   Marco
> >>>
> >>>
> >>>>
> >>>>
> >>>> Cheers,
> >>>> Ahmad
> >>>>
> >>>> -- 
> >>>> Pengutronix e.K.                  |                             |
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> >>>>
> >>>>
> >>>
> >>
> >> -- 
> >> Pengutronix e.K.                  |                             |
> >> Steuerwalder Str. 21              | http://www.pengutronix.de/  |
> >> 31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
> >> Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |
> >>
> >>
> > 
> 
> -- 
> Pengutronix e.K.                  |                             |
> Steuerwalder Str. 21              | http://www.pengutronix.de/  |
> 31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |
> 
> 

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