[PATCH v3 4/8] drm/print: Add drm_printf_indent()

[Noralf Trønnes]

Den 26.10.2017 19.49, skrev Ville Syrjälä:
> On Thu, Oct 26, 2017 at 06:57:27PM +0200, Noralf Trønnes wrote:
>> Add drm_printf_indent() that adds tab indentation according to argument.
>>
>> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
>> ---
>>   drivers/gpu/drm/drm_print.c | 21 +++++++++++++++++++++
>>   include/drm/drm_print.h     |  2 ++
>>   2 files changed, 23 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
>> index 0b3bf476dc4b..dac3ee98b30f 100644
>> --- a/drivers/gpu/drm/drm_print.c
>> +++ b/drivers/gpu/drm/drm_print.c
>> @@ -64,6 +64,27 @@ void drm_printf(struct drm_printer *p, const char *f, ...)
>>   }
>>   EXPORT_SYMBOL(drm_printf);
>>   
>> +/**
>> + * drm_printf_indent - print to a &drm_printer stream with indentation
>> + * @p: the &drm_printer
>> + * @i: indentation
>> + * @f: format string
>> + */
>> +void drm_printf_indent(struct drm_printer *p, unsigned int i, const char *f, ...)
>> +{
>> +	struct va_format vaf;
>> +	va_list args;
>> +
>> +	drm_printf(p, "%.*s", i, "\t\t\t\t\t\t\t\t\t\t");
>> +
>> +	va_start(args, f);
>> +	vaf.fmt = f;
>> +	vaf.va = &args;
>> +	p->printfn(p, &vaf);
>> +	va_end(args);
>> +}
>> +EXPORT_SYMBOL(drm_printf_indent);
> The double printf() is rather unfortunate. Sadly I don't think there's
> any proper way to manipulate a va_list to avoid that.
>
> Hmm. Would it work if we simply make it a macro? Eg.
>
> #define drm_printf_indent(printer, indent, fmt, ...) \
> 	drm_printf((printer), "%.*s" fmt, (indent), "\t\t\t", ##__VA_ARGS__)

The macro worked fine and it looks like a better solution to me.

> The "\t\t\t..." thing is also rather off putting, but I guess it's
> the best we can do if we want to keep it to one printf(). And maybe we
> should have a check in there to make sure we have enought tabs in the
> string to satisfy the indent level, or we just clamp the indent level
> silently to something reasonable?

I put 10 tabs in my suggestion, which should be enough and I think it's
OK to just silently fail to do more. If 10 isn't enough it's easy to add
more for the developer that hits the limit.

Noralf.

> Oh, seeing the \t now reminds me that tabs won't necesarily get printed
> out properly. At least I've seen fbcon just printing some weird blobs
> instead of tabs. Not sure if it's just a matter of having a crappy font
> or what. That said, the state dump code is using tabs already, so I guess
> this wouldn't make it worse at least.
>
>> +
>>   #define DRM_PRINTK_FMT "[" DRM_NAME ":%s]%s %pV"
>>   
>>   void drm_dev_printk(const struct device *dev, const char *level,
>> diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
>> index 7b9c86a6ca3e..73dcd16eca49 100644
>> --- a/include/drm/drm_print.h
>> +++ b/include/drm/drm_print.h
>> @@ -79,6 +79,8 @@ void __drm_printfn_debug(struct drm_printer *p, struct va_format *vaf);
>>   
>>   __printf(2, 3)
>>   void drm_printf(struct drm_printer *p, const char *f, ...);
>> +__printf(3, 4)
>> +void drm_printf_indent(struct drm_printer *p, unsigned int i, const char *f, ...);
>>   
>>   
>>   /**
>> -- 
>> 2.14.2