linux-kernel - Re: [PATCH v8 4/4] serial: pl011: add console matching function

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Date:	Wed, 22 Jun 2016 07:08:33 -0700
From:	Peter Hurley <peter@...leysoftware.com>
To:	Yury Norov <ynorov@...iumnetworks.com>
Cc:	Aleksey Makarov <aleksey.makarov@...aro.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-serial@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	Len Brown <lenb@...nel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Al Stone <ahs3@...hat.com>,
	Christopher Covington <cov@...eaurora.org>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	"Zheng, Lv" <lv.zheng@...el.com>, Mark Salter <msalter@...hat.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Russell King <linux@...linux.org.uk>,
	Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH v8 4/4] serial: pl011: add console matching function



> On Jun 22, 2016, at 5:18 AM, Yury Norov <ynorov@...iumnetworks.com> wrote:
> 
>> On Fri, May 20, 2016 at 04:03:23PM +0300, Aleksey Makarov wrote:
>> This patch adds function pl011_console_match() that implements
>> method match of struct console.  It allows to match consoles against
>> data specified in a string, for example taken from command line or
>> compiled by ACPI SPCR table handler.
>> 
>> Signed-off-by: Aleksey Makarov <aleksey.makarov@...aro.org>
>> Reviewed-by: Peter Hurley <peter@...leysoftware.com>
>> ---
>> drivers/tty/serial/amba-pl011.c | 56 +++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 56 insertions(+)
>> 
>> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
>> index a2aa655..388edc8 100644
>> --- a/drivers/tty/serial/amba-pl011.c
>> +++ b/drivers/tty/serial/amba-pl011.c
>> @@ -2288,12 +2288,68 @@ static int __init pl011_console_setup(struct console *co, char *options)
>>    return uart_set_options(&uap->port, co, baud, parity, bits, flow);
>> }
>> 
>> +/**
>> + *    pl011_console_match - non-standard console matching
>> + *    @co:      registering console
>> + *    @name:      name from console command line
>> + *    @idx:      index from console command line
>> + *    @options: ptr to option string from console command line
>> + *
>> + *    Only attempts to match console command lines of the form:
>> + *        console=pl011,mmio|mmio32,<addr>[,<options>]
>> + *        console=pl011,0x<addr>[,<options>]
>> + *    This form is used to register an initial earlycon boot console and
>> + *    replace it with the amba_console at pl011 driver init.
>> + *
>> + *    Performs console setup for a match (as required by interface)
>> + *    If no <options> are specified, then assume the h/w is already setup.
>> + *
>> + *    Returns 0 if console matches; otherwise non-zero to use default matching
>> + */
>> +static int __init pl011_console_match(struct console *co, char *name, int idx,
>> +                      char *options)
>> +{
>> +    char match[] = "pl011";    /* pl011-specific earlycon name */
>> +    unsigned char iotype;
>> +    unsigned long addr;
>> +    int i;
>> +
>> +    if (strncmp(name, match, 5) != 0)
>> +        return -ENODEV;
>> +
>> +    if (uart_parse_earlycon(options, &iotype, &addr, &options))
>> +        return -ENODEV;
>> +
>> +    /* try to match the port specified on the command line */
>> +    for (i = 0; i < ARRAY_SIZE(amba_ports); i++) {
>> +        struct uart_port *port;
>> +
>> +        if (!amba_ports[i])
>> +            continue;
>> +
>> +        port = &amba_ports[i]->port;
>> +
>> +        if (iotype != UPIO_MEM && iotype != UPIO_MEM32)
>> +            continue;
> 
> So it looks like iotype is constant inside the loop, and UPIO_MEM
> and UPIO_MEM32 too, of course. It means you can move this check out of
> cycle and avoid ports traversing at all in specific case. Am I wrong?
> 

No you're not wrong but I'd prefer if we don't use assumptions like that in port enumeration.


>> +
>> +        if (port->mapbase != addr)
>> +            continue;
>> +
>> +        co->index = i;
>> +        port->cons = co;
>> +        return pl011_console_setup(co, options);
>> +    }
>> +
>> +    return -ENODEV;
>> +}
>> +
>> static struct uart_driver amba_reg;
>> static struct console amba_console = {
>>    .name        = "ttyAMA",
>>    .write        = pl011_console_write,
>>    .device        = uart_console_device,
>>    .setup        = pl011_console_setup,
>> +    .match        = pl011_console_match,
>>    .flags        = CON_PRINTBUFFER,
>>    .index        = -1,
>>    .data        = &amba_reg,
>> -- 
>> 2.8.2