drm: Add drm_puts() to complement drm_printf()

Add drm_puts() for a much faster path to print constant strings
into a drm_printer object with memcpy and friends. This can
have seconds off of really large outputs such as GPU dumps.

If the drm_printer object supports a custom puts function then
use that otherwise fall back to the slower legacy printf call.

v2: Add documentation for drm_puts() per Daniel Vetter

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
[robclark fix minor htmldocs warning]
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/drm_print.c

@@ -122,6 +122,23 @@ void __drm_printfn_debug(struct drm_printer *p, struct va_format *vaf)
 }
 EXPORT_SYMBOL(__drm_printfn_debug);
 
+/**
+ * drm_puts - print a const string to a &drm_printer stream
+ * @p: the &drm printer
+ * @str: const string
+ *
+ * Allow &drm_printer types that have a constant string
+ * option to use it.
+ */
+void drm_puts(struct drm_printer *p, const char *str)
+{
+	if (p->puts)
+		p->puts(p, str);
+	else
+		drm_printf(p, "%s", str);
+}
+EXPORT_SYMBOL(drm_puts);
+
 /**
  * drm_printf - print to a &drm_printer stream
  * @p: the &drm_printer

include/drm/drm_print.h

@@ -69,6 +69,7 @@
 struct drm_printer {
 	/* private: */
 	void (*printfn)(struct drm_printer *p, struct va_format *vaf);
+	void (*puts)(struct drm_printer *p, const char *str);
 	void *arg;
 	const char *prefix;
 };
@@ -80,6 +81,7 @@ 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, ...);
+void drm_puts(struct drm_printer *p, const char *str);
 
 __printf(2, 0)
 /**