Re: [PATCH v3 3/3] printk: fix double printing with earlycon
From: Aleksey Makarov
Date: Wed Mar 08 2017 - 09:52:00 EST
On 03/08/2017 06:33 AM, Sergey Senozhatsky wrote:
Hello,
sorry for the delay.
On (03/07/17 15:54), Aleksey Makarov wrote:
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.
no problems with the enum on its own. errnos probably can also do
the trick.
the way it's defined, however, is a bit unusual and may be
inconvenient - we can add, say, 5 more CONSOLE_MATCH_FOO someday
in the future and match_console() function definition thus will be:
static enum { CONSOLE_MATCH, CONSOLE_MATCH_RETURN, CONSOLE_MATCH_NEXT,
CONSOLE_MATCH_FOO1, CONSOLE_MATCH_FOO2,
CONSOLE_MATCH_FOO3, CONSOLE_MATCH_FOO4,
CONSOLE_MATCH_FOO5}
match_console(struct console *newcon, struct console_cmdline *c)
{
...
}
or something like this
static enum { CONSOLE_MATCH,
CONSOLE_MATCH_RETURN,
CONSOLE_MATCH_NEXT,
CONSOLE_MATCH_FOO1,
CONSOLE_MATCH_FOO2,
CONSOLE_MATCH_FOO3,
CONSOLE_MATCH_FOO4,
CONSOLE_MATCH_FOO5 }
match_console(struct console *newcon, struct console_cmdline *c)
{
..
}
or anything else. which is, to my admittedly imperfect taste, slightly
"unpretty".
I agree that this enum thing does not look good and I have an idea how to
get rid of it completely. The idea is to factor out the braille
code to a separate pass. That way the match function can return a boolean
value.
I am traveling now so I will need some time to
send a new version of this patch.
Thank you
Aleksey Makarov
[..]
+ /*
* 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,
my bad, sorry. I misread the patch: there was another `break' right after
that switch, that you have removed; and I just wrongly concluded that
CONSOLE_MATCH_NEXT would now 'break' from 'default' label *and* `break'
from the console_cmdline loop right after it.
bikeshedding:
may be explicit CONSOLE_MATCH_NEXT test will save us from problems (in
case if match_console() will return more codes someday), may be it won't.
hard to say. 'default: continue' is probably OK. or may be can do without
that 'match' label at all. something like this (_may be_)
for (i = 0, c = console_cmdline; ... ) {
if (preferred_console == i)
continue;
match = match_console(newcon, c);
if (match == CONSOLE_MATCH_NEXT)
continue;
if (match == CONSOLE_MATCH_FOUND)
break;
if (match == CONSOLE_MATCH_STOP)
return;
}
...
CONSOLE_MATCH_RETURN - basically means that we should stop matching.
can we thus rename it to CONSOLE_MATCH_STOP, or similar?
match_console() returned CONSOLE_MATCH_STOP
is a bit better than
match_console() returned CONSOLE_MATCH_RETURN.
isn't it? :)
// I also used CONSOLE_MATCH_FOUND in the example above instead of
// CONSOLE_MATCH. not insisting that CONSOLE_MATCH_FOUND is much
// better than CONSOLE_MATCH though.
-ss