Re: [PATCH v3 3/3] printk: fix double printing with earlycon

[Aleksey Makarov]

On 03/06/2017 03:59 PM, Sergey Senozhatsky wrote:
> On (03/03/17 18:49), Aleksey Makarov wrote:
> [..]
> > +static enum { CONSOLE_MATCH, CONSOLE_MATCH_RETURN, CONSOLE_MATCH_NEXT }
> > +match_console(struct console *newcon, struct console_cmdline *c)
>
> that enum in function return is interesting :)
> can we make it less hackish?

We probably can, but I can not figure out how to do that.
Suggestions will be appreciated.
We should signal 3 different outcomes.
I thought that using standard errnos is not quite desciptive.

> > +	if (!newcon->match ||
> > +	    newcon->match(newcon, c->name, c->index, c->options) != 0) {
> > +		/* default matching */
> > +		BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
> > +		if (strcmp(c->name, newcon->name) != 0)
> > +			return CONSOLE_MATCH_NEXT;
> > +		if (newcon->index >= 0 && newcon->index != c->index)
> > +			return CONSOLE_MATCH_NEXT;
>
> who is checking CONSOLE_MATCH_NEXT?

The caller checks two other values,  this one goes under the default case.
Should I check it explicitly?

> > +		if (newcon->index < 0)
> > +			newcon->index = c->index;
> > +
> > +		if (_braille_register_console(newcon, c))
> > +			return CONSOLE_MATCH_RETURN;
> > +
> > +		if (newcon->setup &&
> > +		    newcon->setup(newcon, c->options) != 0)
> > +			return CONSOLE_MATCH;
> > +	}
> > +
> > +	newcon->flags |= CON_ENABLED;
> > +	return CONSOLE_MATCH;
> > +}
> > +
> >  /*
> >   * The console driver calls this routine during kernel initialization
> >   * to register the console printing procedure with printk() and to
> > @@ -2454,40 +2480,50 @@ void register_console(struct console *newcon)
> >  	}
> >
> >  	/*
> > +	 * Check if this console was set as preferred by command line parameters
> > +	 * or by call to add_preferred_console().  There may be several entries
> > +	 * in the console_cmdline array matching with the same console so we
> > +	 * can not just use the first match.  Instead check the entry pointed
> > +	 * by preferred_console and then all other entries.
> > +	 */
> > +	if (preferred_console >= 0) {
> > +		switch (match_console(newcon,
> > +				      console_cmdline + preferred_console)) {
> > +		case CONSOLE_MATCH:
> > +			if (newcon->flags | CON_ENABLED) {
>
> 			newcon->flags & CON_ENABLED  ?

Sure.  Thank you.

> > +				newcon->flags |= CON_CONSDEV;
> > +				has_preferred = true;
> > +			}
> > +			goto match;
> > +		case CONSOLE_MATCH_RETURN:
> > +			return;
> > +		default:
> > +			break;
> > +		}
> > +	}
> > +
> > +	/*
> >  	 *	See if this console matches one we selected on
> >  	 *	the command line.
> >  	 */
> >  	for (i = 0, c = console_cmdline;
> >  	     i < MAX_CMDLINECONSOLES && c->name[0];
> >  	     i++, c++) {
> > -		if (!newcon->match ||
> > -		    newcon->match(newcon, c->name, c->index, c->options) != 0) {
> > -			/* default matching */
> > -			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
> > -			if (strcmp(c->name, newcon->name) != 0)
> > -				continue;
> > -			if (newcon->index >= 0 &&
> > -			    newcon->index != c->index)
> > -				continue;
> > -			if (newcon->index < 0)
> > -				newcon->index = c->index;
> > -
> > -			if (_braille_register_console(newcon, c))
> > -				return;
> >
> > -			if (newcon->setup &&
> > -			    newcon->setup(newcon, c->options) != 0)
> > -				break;
> > -		}
> > +		if (preferred_console == i)
> > +			continue;
> >
> > -		newcon->flags |= CON_ENABLED;
> > -		if (i == preferred_console) {
> > -			newcon->flags |= CON_CONSDEV;
> > -			has_preferred = true;
> > +		switch (match_console(newcon, c)) {
> > +		case CONSOLE_MATCH:
> > +			goto match;
> > +		case CONSOLE_MATCH_RETURN:
> > +			return;
> > +		default:
> > +			break;
>
> sorry, it was a rather long for me today. need to look more at this.
> for what is now CONSOLE_MATCH_NEXT we used to have continue,

CONSOLE_MATCH is for the case when the console matches against the description,
CONSOLE_MATCH_NEXT - it does not, we should try next,
CONSOLE_MATCH_RETURN - we should return as the braille console is registered now.

> and now we break out of the loop?

`goto match` or just when we have seen all the entries

Thank you
Aleksey Makarov

> 	-ss
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