[U-Boot] [PATCH] serial: Move carriage return before line feed for some serial drivers

[James Chargin]

This is a request for more information.

On 02/24/2016 06:41 PM, Alison Wang wrote:
> In general, a carriage return needs to execute before a line feed.
> The patch is to change some serial drivers based on this rule, such
> as serial_mxc.c, serial_pxa.c, serial_s3c24x0.c and usbtty.c.

You write "In general, a carriage return needs to execute before a line 
feed. The patch is to change some serial drivers based on this rule"

Please provide a reference. I'd probably benefit from deeper knowledge 
of this subject. I had not heard this rule before.

Thank you,
Jim

>
> Signed-off-by: Alison Wang <alison.wang at nxp.com>
> ---
>   drivers/serial/serial_mxc.c     | 8 ++++----
>   drivers/serial/serial_pxa.c     | 8 ++++----
>   drivers/serial/serial_s3c24x0.c | 8 ++++----
>   drivers/serial/usbtty.c         | 7 ++++---
>   4 files changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
> index 51485c0..1563bb3 100644
> --- a/drivers/serial/serial_mxc.c
> +++ b/drivers/serial/serial_mxc.c
> @@ -164,15 +164,15 @@ static int mxc_serial_getc(void)
>
>   static void mxc_serial_putc(const char c)
>   {
> +	/* If \n, also do \r */
> +	if (c == '\n')
> +		serial_putc('\r');
> +
>   	__REG(UART_PHYS + UTXD) = c;
>
>   	/* wait for transmitter to be ready */
>   	while (!(__REG(UART_PHYS + UTS) & UTS_TXEMPTY))
>   		WATCHDOG_RESET();
> -
> -	/* If \n, also do \r */
> -	if (c == '\n')
> -		serial_putc ('\r');
>   }
>
>   /*
> diff --git a/drivers/serial/serial_pxa.c b/drivers/serial/serial_pxa.c
> index 8fbcc10..1eb19ec 100644
> --- a/drivers/serial/serial_pxa.c
> +++ b/drivers/serial/serial_pxa.c
> @@ -156,6 +156,10 @@ void pxa_putc_dev(unsigned int uart_index, const char c)
>   {
>   	struct pxa_uart_regs *uart_regs;
>
> +	/* If \n, also do \r */
> +	if (c == '\n')
> +		pxa_putc_dev(uart_index, '\r');
> +
>   	uart_regs = pxa_uart_index_to_regs(uart_index);
>   	if (!uart_regs)
>   		hang();
> @@ -163,10 +167,6 @@ void pxa_putc_dev(unsigned int uart_index, const char c)
>   	while (!(readl(&uart_regs->lsr) & LSR_TEMT))
>   		WATCHDOG_RESET();
>   	writel(c, &uart_regs->thr);
> -
> -	/* If \n, also do \r */
> -	if (c == '\n')
> -		pxa_putc_dev (uart_index,'\r');
>   }
>
>   /*
> diff --git a/drivers/serial/serial_s3c24x0.c b/drivers/serial/serial_s3c24x0.c
> index d4e7df2..0f0878a 100644
> --- a/drivers/serial/serial_s3c24x0.c
> +++ b/drivers/serial/serial_s3c24x0.c
> @@ -135,14 +135,14 @@ static void _serial_putc(const char c, const int dev_index)
>   {
>   	struct s3c24x0_uart *uart = s3c24x0_get_base_uart(dev_index);
>
> +	/* If \n, also do \r */
> +	if (c == '\n')
> +		serial_putc('\r');
> +
>   	while (!(readl(&uart->utrstat) & 0x2))
>   		/* wait for room in the tx FIFO */ ;
>
>   	writeb(c, &uart->utxh);
> -
> -	/* If \n, also do \r */
> -	if (c == '\n')
> -		serial_putc('\r');
>   }
>
>   static inline void serial_putc_dev(unsigned int dev_index, const char c)
> diff --git a/drivers/serial/usbtty.c b/drivers/serial/usbtty.c
> index 75f0ec3..2e19813 100644
> --- a/drivers/serial/usbtty.c
> +++ b/drivers/serial/usbtty.c
> @@ -434,11 +434,12 @@ void usbtty_putc(struct stdio_dev *dev, const char c)
>   	if (!usbtty_configured ())
>   		return;
>
> -	buf_push (&usbtty_output, &c, 1);
>   	/* If \n, also do \r */
>   	if (c == '\n')
>   		buf_push (&usbtty_output, "\r", 1);
>
> +	buf_push(&usbtty_output, &c, 1);
> +
>   	/* Poll at end to handle new data... */
>   	if ((usbtty_output.size + 2) >= usbtty_output.totalsize) {
>   		usbtty_poll ();
> @@ -498,8 +499,8 @@ void usbtty_puts(struct stdio_dev *dev, const char *str)
>   		n = next_nl_pos (str);
>
>   		if (str[n] == '\n') {
> -			__usbtty_puts (str, n + 1);
> -			__usbtty_puts ("\r", 1);
> +			__usbtty_puts("\r", 1);
> +			__usbtty_puts(str, n + 1);
>   			str += (n + 1);
>   			len -= (n + 1);
>   		} else {
>

-- 
Jim Chargin
AJA Video Systems                       jimc at aja.com
(530) 271-3334                          http://www.aja.com