linux-kernel - Re: [PATCH] earlycon: initialise baud field of earlycon device structure

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Date:   Wed, 16 Aug 2017 11:52:42 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     "robherring2@...il.com" <robherring2@...il.com>
CC:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "Eugeniy.Paltsev@...opsys.com" <Eugeniy.Paltsev@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH] earlycon: initialise baud field of earlycon device
 structure

Hi Rob,

On Tue, 2017-08-15 at 14:26 -0500, Rob Herring wrote:
> On Tue, Aug 15, 2017 at 12:21 PM, Eugeniy Paltsev
> <Eugeniy.Paltsev@...opsys.com> wrote:
> > [snip]
> > @@ -282,7 +283,15 @@ int __init of_setup_earlycon(const struct
> > earlycon_id *match,
> >                 }
> >         }
> > 
> > +       val = of_get_flat_dt_prop(node, "baud", NULL);
> 
> No, we already have a defined way to set the baud, we don't need a
> property in addition. Plus you didn't document it.

I guess by defined way to set the baud you mean setting baud after
device alias
in stdout-path property (like stdout-path = "serial:115200n8"), right?

The idea was to reuse "baud" property from serial node to set the
earlycon baud:

chosen {
    ...
    stdout-path = &serial;
};

serial: uart@... {
    ...
    baud = <115200>;   /* Get baud from here */
};

> > +       if (val)
> > +               early_console_dev.baud = be32_to_cpu(*val);
> > +
> >         if (options) {
> > +               err = kstrtoul(options, 10, &baud);
> > +               if (!err)
> > +                       early_console_dev.baud = baud;
> 
> This seems fine to do here, but then we should also parse the other
> standard options here too. And we should make sure we're not doing it
> twice.
I added only baud parsing here because we parse only baud from standard
options
when register_earlycon is used. (see parse_options function which is
called
from register_earlycon)

But I can add other standard options parsing here (probably using
uart_parse_options + uart_set_options). 
What do you think?

> > +
> >                 strlcpy(early_console_dev.options, options,
> >                         sizeof(early_console_dev.options));
> >         }
> > --
> > 2.9.3
-- 
 Eugeniy Paltsev