linux-kernel - Re: [PATCH v4 1/5] RISC-V: Add stubs for sbi_console

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Message-ID: <313e9a3e-0fe5-45e1-a164-1d55fb52898a@sifive.com>
Date:   Thu, 23 Nov 2023 08:45:13 -0600
From:   Samuel Holland <samuel.holland@...ive.com>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Conor Dooley <conor@...nel.org>,
        Andrew Jones <ajones@...tanamicro.com>,
        linux-riscv@...ts.infradead.org, linux-serial@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Subject: Re: [PATCH v4 1/5] RISC-V: Add stubs for
 sbi_console_putchar/getchar()

Hi Anup,

On 2023-11-23 4:38 AM, Anup Patel wrote:
> On Wed, Nov 22, 2023 at 4:06 AM Samuel Holland
> <samuel.holland@...ive.com> wrote:
>> On 2023-11-17 9:38 PM, Anup Patel wrote:
>>> The functions sbi_console_putchar() and sbi_console_getchar() are
>>> not defined when CONFIG_RISCV_SBI_V01 is disabled so let us add
>>> stub of these functions to avoid "#ifdef" on user side.
>>>
>>> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
>>> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
>>> ---
>>>  arch/riscv/include/asm/sbi.h | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>>> index 0892f4421bc4..66f3933c14f6 100644
>>> --- a/arch/riscv/include/asm/sbi.h
>>> +++ b/arch/riscv/include/asm/sbi.h
>>> @@ -271,8 +271,13 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
>>>                       unsigned long arg3, unsigned long arg4,
>>>                       unsigned long arg5);
>>>
>>> +#ifdef CONFIG_RISCV_SBI_V01
>>>  void sbi_console_putchar(int ch);
>>>  int sbi_console_getchar(void);
>>> +#else
>>> +static inline void sbi_console_putchar(int ch) { }
>>> +static inline int sbi_console_getchar(void) { return -ENOENT; }
>>
>> "The SBI call returns the byte on success, or -1 for failure."
>>
>> So -ENOENT is not really an appropriate value to return here.
> 
> Actually, I had -1 over here previously but based on GregKH's
> suggestion, we are now returning proper Linux error code here.
> 
> Also, all users of sbi_console_getchar() onlyl expect a negative
> value upon error so better to return proper Linux error code.

Alright, makes sense to me.

Regards,
Samuel