linux-kernel - Re: [PATCH v6 07/24] RISC-V: Use the minor version mask while computing sbi version

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Date: Tue, 16 Apr 2024 01:31:27 -0700
From: Atish Patra <atishp@...osinc.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: linux-kernel@...r.kernel.org, Ajay Kaher <ajay.kaher@...adcom.com>,
 Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Alexey Makhalov <alexey.amakhalov@...adcom.com>,
 Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 Conor Dooley <conor.dooley@...rochip.com>, Juergen Gross <jgross@...e.com>,
 kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
 linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
 Mark Rutland <mark.rutland@....com>, Palmer Dabbelt <palmer@...belt.com>,
 Paolo Bonzini <pbonzini@...hat.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Shuah Khan <shuah@...nel.org>,
 virtualization@...ts.linux.dev, Will Deacon <will@...nel.org>, x86@...nel.org
Subject: Re: [PATCH v6 07/24] RISC-V: Use the minor version mask while
 computing sbi version

On 4/15/24 06:06, Andrew Jones wrote:
> On Wed, Apr 10, 2024 at 05:07:35PM -0700, Atish Patra wrote:
>> As per the SBI specification, minor version is encoded in the
>> lower 24 bits only. Make sure that the SBI version is computed
>> with the appropriate mask.
>>
>> Currently, there is no minor version in use. Thus, it doesn't
>> change anything functionality but it is good to be compliant with
>> the specification.
>>
>> Signed-off-by: Atish Patra <atishp@...osinc.com>
>> ---
>>   arch/riscv/include/asm/sbi.h | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> index f31650b10899..935b082d6a6c 100644
>> --- a/arch/riscv/include/asm/sbi.h
>> +++ b/arch/riscv/include/asm/sbi.h
>> @@ -367,8 +367,8 @@ static inline unsigned long sbi_minor_version(void)
>>   static inline unsigned long sbi_mk_version(unsigned long major,
>>   					    unsigned long minor)
>>   {
>> -	return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
>> -		SBI_SPEC_VERSION_MAJOR_SHIFT) | minor;
>> +	return ((major & SBI_SPEC_VERSION_MAJOR_MASK) << SBI_SPEC_VERSION_MAJOR_SHIFT
>> +		| (minor & SBI_SPEC_VERSION_MINOR_MASK));
> 
> The previous version had ((major & major_mask) << major_shift) | minor
> (parentheses around all the major bits before the OR). Now we have
> parentheses around everything, which aren't necessary, and no longer

We have to use parentheses around | to avoid compiler warnings 
(-Wparentheses)

Are you only concerned about the outer parentheses ? I have removed it.

> have them around all the major bits before the OR. We don't need the
> parentheses around the major bits, since shift has higher precedence
> than OR, but I'd probably keep them.
> 

Is this what you prefer?

return ((major & SBI_SPEC_VERSION_MAJOR_MASK) << 
SBI_SPEC_VERSION_MAJOR_SHIFT) | (minor & SBI_SPEC_VERSION_MINOR_MASK); 

> Otherwise,
> 
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
> 
>>   }
>>   
>>   int sbi_err_map_linux_errno(int err);
>> -- 
>> 2.34.1
>>
> 
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