linux-kernel - Re: [PATCH 03/14] mailbox: pcc: Drop unnecessary endianness conversion of pcc

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Message-ID: <f414e0e7-6781-000b-1987-2e3c13311c55@huawei.com>
Date: Thu, 6 Mar 2025 11:50:26 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: Sudeep Holla <sudeep.holla@....com>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Jassi Brar
	<jassisinghbrar@...il.com>, Adam Young <admiyo@...amperecomputing.com>
Subject: Re: [PATCH 03/14] mailbox: pcc: Drop unnecessary endianness
 conversion of pcc_hdr.flags


在 2025/3/5 18:36, Sudeep Holla 写道:
> On Wed, Mar 05, 2025 at 12:02:13PM +0800, lihuisong (C) wrote:
>> 在 2025/3/3 18:51, Sudeep Holla 写道:
>>> The Sparse static checker flags a type mismatch warning related to
>>> endianness conversion:
>>>
>>>     |  warning: incorrect type in argument 1 (different base types)
>>>     |     expected restricted __le32 const [usertype] *p
>>>     |     got unsigned int *
>>>
>>> This is because an explicit endianness conversion (le32_to_cpu()) was
>>> applied unnecessarily to a pcc_hdr.flags field that is already in
>>> little-endian format.
>>>
>>> The PCC driver is only enabled on little-endian kernels due to its
>>> dependency on ACPI and EFI, making the explicit conversion unnecessary.
>> How to confirm ACPI works only on little-endian?
> Sorry I didn't notice this question. ACPI depends on ARCH_SUPPORTS_ACPI
> and it is selected only from EFI which is disabled if CPU_BIG_ENDIAN=y
>
got it. I found it.
> .