Re: [PATCH v6 01/15] emul/vuart: introduce framework for UART emulators

[dmukhin@xen.org]

On Mon, Sep 08, 2025 at 11:29:03AM +0300, Mykola Kvach wrote:
> On Sat, Sep 6, 2025 at 2:27 AM <dmukhin@xen.org> wrote:
[..]
> > +++ b/xen/common/emul/vuart/Kconfig
> > @@ -0,0 +1,6 @@
> > +config VUART_FRAMEWORK
> > +       bool
> 
> If VUART_FRAMEWORK has no dependencies, it can be enabled on any
> architecture. For example, I tried enabling it on arm64 and the build
> fails:
> 
>   ./include/xen/vuart.h:26:8: error: redefinition of ‘struct vuart’
> 
> Should this config be restricted (e.g. "depends on X86") or the code
> adjusted to handle non-x86 architectures properly?

Yes, missed that; the code is for x86 only for now.
`struct vuart` on Arm corresponds to simple MMIO-based UART emulator for
hwdom's earlyprintk.

Arm part is pending:
  https://lore.kernel.org/xen-devel/20250624035443.344099-1-dmukhin@ford.com/

Most of the feedback resolved locally, but I need to wait for the other series to land

[..]
> > +static const struct vuart_emulator *
> > +vuart_match_by_compatible(const struct domain *d, const char *compat)
> > +{
> > +    const struct vuart_emulator *emulator;
> > +
> > +    for_each_emulator(emulator)
> > +        if ( emulator->compatible &&
> > +             !strncmp(compat, emulator->compatible,
> > +                      strlen(emulator->compatible)) )
> > +            return emulator;
> > +
> > +    return NULL;
> > +}
> > +
> > +const static struct vuart *
> > +vuart_find_by_console_permission(const struct domain *d)
> 
> During the first review of this patch I thought you planned to add a
> searching procedure into this and the next function in one of the later
> commits. However, looking at the series now, it seems these functions
> remain unchanged and don’t actually perform any searching.
> 
> Do you think the current names are accurate, or would it make sense to
> rename them to better reflect their purpose?

Arm has two vUART emulators enabled by default, so there will be at least two
vUARTs and some search in vuart.c.

I scoped x86 portion of the change into the current series, Arm is to follow,
since I have pending series to plumb vpl011 (i.e. SBSA) and hwdom vuart (i.e.
early dtuart) into that new framework. There will be some adjustments in
vuart.c