linux-kernel - Re: [PATCH v2 2/3] acpi: allow building without CONFIG_HAS

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Message-Id: <de65a5c8-1bbd-47b3-9dc5-de4ad93c41b8@app.fastmail.com>
Date: Fri, 11 Oct 2024 09:59:46 +0000
From: "Arnd Bergmann" <arnd@...db.de>
To: "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
 "Arnd Bergmann" <arnd@...nel.org>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, "Len Brown" <lenb@...nel.org>,
 "Mario Limonciello" <mario.limonciello@....com>,
 "Jarred White" <jarredwhite@...ux.microsoft.com>,
 "Perry Yuan" <perry.yuan@....com>,
 "Easwar Hariharan" <eahariha@...ux.microsoft.com>,
 linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] acpi: allow building without CONFIG_HAS_IOPORT

On Fri, Oct 11, 2024, at 09:53, Andy Shevchenko wrote:
> On Fri, Oct 11, 2024 at 06:18:18AM +0000, Arnd Bergmann wrote:
>
> ...
>
>> +	if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
>> +		*value = BIT_MASK(width);
>> +		return AE_NOT_IMPLEMENTED;
>
> Perhaps it has already been discussed, but why do we need to file value with
> semi-garbage when we know it's invalid anyway?

It's not strictly necessary, just precaution for possible callers
that use the resulting data without checking the error code.

The all-ones data is what an x86 PC would see when an I/O
port is read that is not connected to any device.

     Arnd