ASoC: soc-dapm: Add helper for comparing widget name

Some drivers use one event callback for multiple widgets but still need
to perform a bit different actions based on actual widget. This is done
by comparing widget name, however drivers tend to miss possible name
prefix. Add a helper to solve common mistakes.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

include/sound/soc-dapm.h

···
 
 int snd_soc_dapm_update_dai(struct snd_pcm_substream *substream,
 			    struct snd_pcm_hw_params *params, struct snd_soc_dai *dai);
+int snd_soc_dapm_widget_name_cmp(struct snd_soc_dapm_widget *widget, const char *s);
 
 /* dapm path setup */
 int snd_soc_dapm_new_widgets(struct snd_soc_card *card);

sound/soc/soc-component.c

···
 	char name[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
 	struct snd_kcontrol *kctl;
 
+	/* When updating, change also snd_soc_dapm_widget_name_cmp() */
 	if (component->name_prefix)
 		snprintf(name, ARRAY_SIZE(name), "%s %s", component->name_prefix, ctl);
 	else

sound/soc/soc-dapm.c

···
 }
 EXPORT_SYMBOL_GPL(snd_soc_dapm_update_dai);
 
+int snd_soc_dapm_widget_name_cmp(struct snd_soc_dapm_widget *widget, const char *s)
+{
+	struct snd_soc_component *component = snd_soc_dapm_to_component(widget->dapm);
+	const char *wname = widget->name;
+
+	if (component->name_prefix)
+		wname += strlen(component->name_prefix) + 1; /* plus space */
+
+	return strcmp(wname, s);
+}
+EXPORT_SYMBOL_GPL(snd_soc_dapm_widget_name_cmp);
+
 /*
  * dapm_update_widget_flags() - Re-compute widget sink and source flags
  * @w: The widget for which to update the flags