Re: [PATCH] xen/acpi: Don't fail if SPCR table is absent

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.10.2020 19:13, Elliott Mitchell wrote:
> On Thu, Oct 22, 2020 at 09:42:17AM +0200, Jan Beulich wrote:
>> On 22.10.2020 00:12, Elliott Mitchell wrote:
>>> --- a/xen/arch/arm/acpi/domain_build.c
>>> +++ b/xen/arch/arm/acpi/domain_build.c
>>> @@ -42,17 +42,18 @@ static int __init acpi_iomem_deny_access(struct domain 
>>> *d)
>>>      status = acpi_get_table(ACPI_SIG_SPCR, 0,
>>>                              (struct acpi_table_header **)&spcr);
>>>  
>>> -    if ( ACPI_FAILURE(status) )
>>> +    if ( ACPI_SUCCESS(status) )
>>>      {
>>> -        printk("Failed to get SPCR table\n");
>>> -        return -EINVAL;
>>> +        mfn = spcr->serial_port.address >> PAGE_SHIFT;
>>> +        /* Deny MMIO access for UART */
>>> +        rc = iomem_deny_access(d, mfn, mfn + 1);
>>> +        if ( rc )
>>> +            return rc;
>>> +    }
>>> +    else
>>> +    {
>>> +        printk("Failed to get SPCR table, Xen console may be 
>>> unavailable\n");
>>>      }
>>
>> Nit: While I see you've got Stefano's R-b already, I Xen we typically
>> omit the braces here.
> 
> Personally, I prefer that myself, but was unsure of the preference here.
> I've seen multiple projects which *really* dislike using having brackets
> for some clauses, but not others (ie they want either all clauses with or
> all clauses without; instead of only if required).
> 
> I sent what I thought was the more often used format.  (I also like tabs,
> and dislike having so many spaces; alas my preferences are apparently
> uncommon)

"More often used" doesn't matter when there's an explicit statement
about this in ./CODING_STYLE: "Braces should be omitted for blocks
with a single statement." Yes, there are projects requiring all
if/else-if belonging together to consistently use or not use braces.
But there's explicitly no such statement in our doc. (Along these
lines, dislike of spaces [and favoring tabs] also doesn't matter, as
again the doc is explicit about it.)

Jan