[U-Boot] putc

[Simon Glass]

Hi Martin,

On 30 October 2014 00:45, Martin Dorwig <dorwig at tetronik.com> wrote:
> Am Mittwoch, 29. Oktober 2014, 13:03:41 schrieben Sie:
>> Hi Martin,
>>
>> On 28 October 2014 07:23, Martin Dorwig <dorwig at tetronik.com> wrote:
>> > Hello,
>> > after updating u-boot from git v2014.10
>> > i just noticed that my standalone  application outputs garbage using putc.
>> > after some investigation i found that the gd->jt[XF_putc] is assigned a
>> > dev->putc pointer in "common/console.c function console_setfile"
>> >
>> > the dev->putc is declared in include/stdio_dev.h as
>> > void (*putc)(struct stdio_dev *dev, const char c);
>> >
>> > int include/exports.h this function is declared as
>> > void putc(const char);
>> >
>> > this was introduced with commit id
>> > 709ea543b92489e7729d2d7ddd6c9f451e52158c
>>
>> That's unfortunate. Is the stdio device pointer available in the
>> standalone application?
>>
>> Perhaps gd->jt should point to a structure of strongly-typed
>> functions? Then we would get a build error in this case.
>>
>> Regards,
>> Simon
>
> What is the motivation to override the jumptable slots ?
> Why can't they be untouched like this
> gd->jt[XF_getc] = getc;
> gd->jt[XF_tstc] = tstc;
> gd->jt[XF_putc] = putc;
> gd->jt[XF_puts] = puts;
> redirection of the console to another device is honored in the implementation
> of the functions themselves.
> for example the putc function:
> it calls pre_console_putc before a console is present
> if GD_FLG_DEVINIT is set, it calls fputc(stdout,c) which calls
> console_putc(stdout,c) which in turn calls stdio_devices[stdout]-
>>putc(stdio_devices[file], c);
> else it calls serial_putc(c)

I have taken a bit of a look at this.

I have not actually touched the jumptable slots. The one you mention
was assigned to dev->putc() before and after. The problem is that now
dev->putc() has two parameters, the first being 'dev'.

dev->putc() is the device's putc function - typically the serial port
or a display.

The putc() function you mention is the console out, that outputs to
all stdout devices.

So yes we could change the bahaviour so that it calls putc(). I think
this will work, and it probably isn't going to result in a change in
behaviour for many boards since they only have a single stdout.

Alternatively we could require the stdio device parameter to be passed
in. I'm not sure that will work though - how will the external program
get at it?

In any case, teh void *gd->jt[] is not serving our purpose here - it
should be changed to proper function pointer types so that the
compiler can check that this sort of thing doesn't happen.

Please let me know what you think should be done here.

Regards,
Simon