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

[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 "\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?

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

-- 
Ville Syrjälä
Intel OTC