linux-kernel - Re: [PATCH v4 4/5] tty: Add SBI debug console support to HVC SBI driver

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Date:   Mon, 20 Nov 2023 08:16:00 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Anup Patel <apatel@...tanamicro.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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,
        Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH v4 4/5] tty: Add SBI debug console support to HVC SBI
 driver

On 18. 11. 23, 4:38, Anup Patel wrote:
> diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_riscv_sbi.c
> index 31f53fa77e4a..697c981221b5 100644
> --- a/drivers/tty/hvc/hvc_riscv_sbi.c
> +++ b/drivers/tty/hvc/hvc_riscv_sbi.c
...
> -static int __init hvc_sbi_console_init(void)
> +static int hvc_sbi_dbcn_tty_get(uint32_t vtermno, char *buf, int count)
>   {
> -	hvc_instantiate(0, 0, &hvc_sbi_ops);
> +	phys_addr_t pa;
> +
> +	if (is_vmalloc_addr(buf)) {

I wonder, where does this buf come from, so that you have to check for 
vmalloc?

> +		pa = page_to_phys(vmalloc_to_page(buf)) + offset_in_page(buf);
> +		if (PAGE_SIZE < (offset_in_page(buf) + count))

Am I the only one who would prefer:
   if (count + offset_in_page(buf) > PAGE_SIZE)
?

> +			count = PAGE_SIZE - offset_in_page(buf);
> +	} else {
> +		pa = __pa(buf);
> +	}
> +
> +	return sbi_debug_console_read(count, pa);
> +}


thanks,
-- 
js
suse labs