Re: [PATCH v5 1/9] drivers/char: separate dbgp=xhci to dbc=xhci option

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Aug 26, 2022 at 04:20:52PM +0200, Jan Beulich wrote:
> On 26.08.2022 13:46, Marek Marczykowski-Górecki wrote:
> > On Thu, Aug 25, 2022 at 05:44:54PM +0200, Jan Beulich wrote:
> >> On 22.08.2022 17:27, Marek Marczykowski-Górecki wrote:
> >>> This allows configuring EHCI and XHCI consoles separately,
> >>> simultaneously.
> >>>
> >>> Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
> >>
> >> But was I maybe confused, and much less of a change would suffice? After
> >> all ...
> >>
> >>> --- a/xen/drivers/char/xhci-dbc.c
> >>> +++ b/xen/drivers/char/xhci-dbc.c
> >>> @@ -1058,9 +1058,9 @@ static struct xhci_dbc_ctx ctx __aligned(16);
> >>>  static uint8_t out_wrk_buf[DBC_WORK_RING_CAP];
> >>>  static struct xhci_string_descriptor str_buf[DBC_STRINGS_COUNT];
> >>>  
> >>> -static char __initdata opt_dbgp[30];
> >>> +static char __initdata opt_dbc[30];
> >>>  
> >>> -string_param("dbgp", opt_dbgp);
> >>> +string_param("dbc", opt_dbc);
> >>>  
> >>>  void __init xhci_dbc_uart_init(void)
> >>>  {
> >>> @@ -1068,25 +1068,25 @@ void __init xhci_dbc_uart_init(void)
> >>>      struct dbc *dbc = &uart->dbc;
> >>>      const char *e;
> >>>  
> >>> -    if ( strncmp(opt_dbgp, "xhci", 4) )
> >>> +    if ( strncmp(opt_dbc, "xhci", 4) )
> >>>          return;
> >>
> >> ... this already avoids mixing up who's going to parse what. So right
> >> now I think that ...
> >>
> >>> @@ -1102,7 +1102,7 @@ void __init xhci_dbc_uart_init(void)
> >>>      dbc->dbc_str = str_buf;
> >>>  
> >>>      if ( dbc_open(dbc) )
> >>> -        serial_register_uart(SERHND_DBGP, &dbc_uart_driver, &dbc_uart);
> >>> +        serial_register_uart(SERHND_DBC, &dbc_uart_driver, &dbc_uart);
> >>>  }
> >>
> >> ... this and other SERHND_* related changes are enough, and there's no
> >> need for a separate "dbc=" option.
> > 
> > But then you wouldn't be able to configure "dbgp=ehci dbgp=xhci" as
> > one would override the other, no?
> 
> Not as long as both use string_param(), true. They'd need to both become
> custom_param(), doing at least some basic parsing right away.
> 
> But using two such options at the same time isn't of interest anyway
> without your multiple-serial-consoles change, so possibly not of
> immediate need (unless someone comes forward expressing interest and
> actually approving that change of yours).

Then why change at all? Since you can configure only one (dbgp=ehci _or_
dbgp=xhci), then there is not ambiguity what "console=dbgp" means.
Separating SERHND_DBC from SERHND_DBGP would IMO make sense only if you
can actually use them both (even if not both for console, but for
example one for debugger).

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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