linux-kernel - Re: [PATCH 06/15] serial: 8250_ingenic: Parse earlycon options

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Date:   Thu, 8 Jun 2017 09:31:13 +0200
From:   Marcin Nowakowski <marcin.nowakowski@...tec.com>
To:     Paul Cercueil <paul@...pouillou.net>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>
CC:     Paul Burton <paul.burton@...tec.com>,
        Maarten ter Huurne <maarten@...ewalker.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mips@...ux-mips.org>, <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 06/15] serial: 8250_ingenic: Parse earlycon options

Hi Paul,

On 07.06.2017 22:04, Paul Cercueil wrote:
> In the devicetree, it is possible to specify the baudrate, parity,
> bits, flow of the early console, by passing a configuration string like
> this:
> 
> aliases {
> 	serial0 = &uart0;
> };
> 
> chosen {
> 	stdout-path = "serial0:57600n8";
> };
> 
> This, for instance, will configure the early console for a baudrate of
> 57600 bps, no parity, and 8 bits per baud.
> 
> This patches implements parsing of this configuration string in the
> 8250_ingenic driver, which previously just ignored it.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>   drivers/tty/serial/8250/8250_ingenic.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_ingenic.c b/drivers/tty/serial/8250/8250_ingenic.c
> index b31b2ca552d1..59f3e632df49 100644
> --- a/drivers/tty/serial/8250/8250_ingenic.c
> +++ b/drivers/tty/serial/8250/8250_ingenic.c
> @@ -99,14 +99,24 @@ static int __init ingenic_early_console_setup(struct earlycon_device *dev,
>   					      const char *opt)
>   {
>   	struct uart_port *port = &dev->port;
> -	unsigned int baud, divisor;
> +	unsigned int divisor;
> +	int baud = 115200;
>   
>   	if (!dev->port.membase)
>   		return -ENODEV;
>   
> +	if (opt) {
> +		char options[256];
> +		unsigned int parity, bits, flow; /* unused for now */
> +
> +		strlcpy(options, opt, sizeof(options));

Rather than adding this extra local copy maybe you could instead:

-void uart_parse_options(char *options, int *baud, int *parity, int *bits,
+void uart_parse_options(const char *options, int *baud, int *parity, 
int *bits,

I cannot see any reason why uart_parse_options shouldn't take 'const 
char *options' as an argument.

> +		uart_parse_options(options, &baud, &parity, &bits, &flow);
> +	}
> +
>   	ingenic_early_console_setup_clock(dev);
>   
> -	baud = dev->baud ?: 115200;
> +	if (dev->baud)
> +		baud = dev->baud;
>   	divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * baud);
>   
>   	early_out(port, UART_IER, 0);
> 


Marcin