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

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Message-ID: <CAK9=C2U9aJDDd0JUhRqyLCF3dfyY5QBUrgyH+PKsT+pUKiB1xQ@mail.gmail.com>
Date:   Thu, 23 Nov 2023 16:08:36 +0530
From:   Anup Patel <apatel@...tanamicro.com>
To:     Samuel Holland <samuel.holland@...ive.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()

On Wed, Nov 22, 2023 at 4:06 AM Samuel Holland
<samuel.holland@...ive.com> wrote:
>
> Hi Anup,
>
> 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.

>
> Regards,
> Samuel
>
> > +#endif
> >  long sbi_get_mvendorid(void);
> >  long sbi_get_marchid(void);
> >  long sbi_get_mimpid(void);
>

Regards,
Anup