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Re: [PATCH 1/3] cmdline: Document console=dtuart option
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Wed, 2 Sep 2026 13:12:13 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger@xxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 02 Sep 2026 11:12:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02-Sep-26 10:55, Jan Beulich wrote:
> On 02.09.2026 09:36, Michal Orzel wrote:
>> Document the default console= option on Arm and RISC-V that is
>> "dtuart" indicating a generic UART parsed from a device tree or
>> ACPI SPCR table. This serial utilizes SERHND_DTUART handle.
>>
>> Take the opportunity to:
>> - fix documented x86 default to vga to match OPT_CONSOLE_STR,
>
> I first wanted to object to this part, as I was sure this used to be
> "com1,vga". Yet indeed it's been almost 19 years ago when this was
> changed (92877a1f9ab2 ["x86: Auto-probe the serial port baud rate if
> 'com1' or 'com2' is"]).
>
>> - mark dtuart option as available on RISC-V,
>> - document fall back to /chosen/stdout-path.
>>
>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>
>> --- a/docs/misc/xen-command-line.pandoc
>> +++ b/docs/misc/xen-command-line.pandoc
>> @@ -430,9 +430,10 @@ The following are examples of correct specifications:
>> Specify the size of the console ring buffer.
>>
>> ### console
>> -> `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | ehci | xhci | none
>> ]`
>> +> `= List of [ vga | com1[H,L] | com2[H,L] | pv | dbgp | ehci | xhci |
>> dtuart | none ]`
>>
>> -> Default: `console=com1,vga`
>> +> Default (x86): `console=vga`
>> +> Default (Arm, RISC-V): `console=dtuart`
>
> Any reason to not also cover PPC here?
While PPC sets OPT_CONSOLE_STR to "dtuart", it does not select
CONFIG_GENERIC_UART_INIT that compiles in the uart-init.c which is what really
matters to decide whether dtuart is supported or not.
~Michal
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