Re: [PATCH] RISC-V: virt: This is a "sifive,test1" test finisher

[Alistair Francis]

On Wed, Nov 20, 2019 at 6:40 PM Palmer Dabbelt <address@hidden> wrote:
>
> On Sun, 10 Nov 2019 13:10:33 PST (-0800), address@hidden wrote:
> > On Fri, Nov 08, 2019 at 10:13:16AM -0800, Palmer Dabbelt wrote:
> >> On Fri, 08 Nov 2019 10:04:47 PST (-0800), Peter Maydell wrote:
> >> > On Fri, 8 Nov 2019 at 17:15, Alistair Francis <address@hidden> wrote:
> >> > >
> >> > > On Fri, Nov 8, 2019 at 9:05 AM Palmer Dabbelt <address@hidden> wrote:
> >> > > >
> >> > > > The test finisher implements the reset command, which means it's a
> >> > > > "sifive,test1" device.  This is a backwards compatible change, so 
> >> > > > it's
> >> > > > also a "sifive,test0" device.  I copied the odd idiom for adding a
> >> > > > two-string compatible field from the ARM virt board.
> >> > > >
> >> > > > Fixes: 9a2551ed6f ("riscv: sifive_test: Add reset functionality")
> >> > > > Signed-off-by: Palmer Dabbelt <address@hidden>
> >> > > > Signed-off-by: Palmer Dabbelt <address@hidden>
> >> > > > ---
> >> > > >  hw/riscv/virt.c | 5 ++++-
> >> > > >  1 file changed, 4 insertions(+), 1 deletion(-)
> >> > > >
> >> > > > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> >> > > > index 23f340df19..74f2dce81c 100644
> >> > > > --- a/hw/riscv/virt.c
> >> > > > +++ b/hw/riscv/virt.c
> >> > > > @@ -359,7 +359,10 @@ static void create_fdt(RISCVVirtState *s, const 
> >> > > > struct MemmapEntry *memmap,
> >> > > >      nodename = g_strdup_printf("/test@%lx",
> >> > > >          (long)memmap[VIRT_TEST].base);
> >> > > >      qemu_fdt_add_subnode(fdt, nodename);
> >> > > > -    qemu_fdt_setprop_string(fdt, nodename, "compatible", 
> >> > > > "sifive,test0");
> >> > > > +    {
> >> > > > +        const char compat[] = "sifive,test1\0sifive,test0";
> >> > >
> >> > > Does this really work? Why not use qemu_fdt_setprop_cells()?
> >> > >
> >> > > Alistair
> >> > >
> >> > > > +        qemu_fdt_setprop(fdt, nodename, "compatible", compat, 
> >> > > > sizeof(compat));
> >> > > > +    }
> >> >
> >> > qemu_fdt_setprop_cells() is for "set this property to
> >> > contain this list of 32-bit integers" (and it does a byteswap
> >> > of each 32-bit value from host to BE). That's not what
> >> > you want for a string (or a string list, which is what
> >> > we have here).
> >> >
> >> > Cc'ing David Gibson who's our device tree expert to see if there's
> >> > a nicer way to write this. Oddly, given that it's used in the
> >> > ubiquitous 'compatible' prop, the dtc Documentation/manual.txt
> >> > doesn't say anything about properties being able to be
> >> > 'string lists', only 'strings', '32 bit numbers', 'lists of
> >> > 32-bit numbers' and 'byte sequences'. You have to dig through
> >> > the header file comments to deduce that a string list is
> >> > represented by a string with embedded NULs separating
> >> > each list item.
> >>
> >> I copied this from hw/arm/virt.c, but messed up.  There they use
> >>
> >>        const char compat[] = "arm,armv8-timer\0arm,armv7-timer";
> >>        qemu_fdt_setprop(vms->fdt, "/timer", "compatible",
> >>                         compat, sizeof(compat));
> >
> > I'm not sure what you're saying is messed up.  AFAICT, this matches
> > the code you have above, and both should be correct.
>
> Sorry, I must have been hallucinating.  For some reason I though I wrote
> qemu_fdt_setprop_string(... compat).
>
> I'd like to take this for 4.2 if possible, but I don't think I have a
> reviewed-by (I just got my email set up on my Google computer, so it might be
> messy for a bit).  I'm happy to submit the cleaner valist version after 4.2, 
> as
> per Peter's suggestion.
>
> Alistair: are you OK with this?

Yeah, that works for me.

For 5.0 we can then merge Anup's patch and your series improving the
multi compat support.

Reviewed-by: Alistair Francis <address@hidden>

Alistair

>
> >> I'll send a v2, but I'd be happy to add some sort of setprop_stringlist
> >> function.  Maybe we just indicate the length with two '\0's?  IIRC that's
> >> how other similar-looking data structures are encoded.
> >>
> >
> > --
> > David Gibson                  | I'll have my music baroque, and my code
> > david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> > _other_
> >                               | _way_ _around_!
> > http://www.ozlabs.org/~dgibson