linux-kernel - Re: [PATCH] tty/serial: emit CR before NL in RISC-V SBL console

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Date:   Thu, 10 Jan 2019 21:47:07 +0530
From:   Anup Patel <anup@...infault.org>
To:     Andreas Schwab <schwab@...e.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atish.patra@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Rob Herring <robh@...nel.org>, linux-riscv@...ts.infradead.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty/serial: emit CR before NL in RISC-V SBL console

On Thu, Jan 10, 2019 at 8:56 PM Andreas Schwab <schwab@...e.de> wrote:
>
> On Jan 10 2019, Anup Patel <anup@...infault.org> wrote:
>
> > Instead of doing '\n' handling here, we should do it in BBL or
> > OpenSBI (i.e. SBI runtime firmware) otherwise all users of
> > SBI_CONSOLE_PUTCHAR (namely, Linux, FreeBSD,
> > FreeRTOS, U-Boot S-mode, etc) will endup having '\n'
> > handling.
>
> I don't think the serial driver should do NLCR handling on its own,
> without being instructed by the tty layer.  Since the earlycon does not
> have a tty layer, it needs to handle it explicitly.

I tried to investigate more. What you suggest is correct
but we should use uart_console_write() API.

Instead of explicitly doing NLCR here, we should do
something as follows:

static void sbi_putc(struct uart_port *port, int c)
{
    sbi_console_putchar(c);
}

static void sbi_console_write(struct console *con,
                                               const char *s, unsigned n)
{
    struct earlycon_device *dev = con->data;
    uart_console_write(&dev->port, s, n, sbi_putc);
}

The uart_console_write() does the NLCR handling.

Regards,
Anup