ALSA: add dummy function to support shared mmap in nommu Blackfin arch

Cc: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: NCliff Cai <cliff.cai@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@perex.cz>

sound/core/pcm_native.c

@@ -3385,6 +3385,17 @@ static int snd_pcm_hw_params_old_user(struct snd_pcm_substream *substream,
 }
 #endif /* CONFIG_SND_SUPPORT_OLD_API */
 
+#ifndef CONFIG_MMU
+unsigned long dummy_get_unmapped_area(struct file *file, unsigned long addr,
+				      unsigned long len, unsigned long pgoff,
+				      unsigned long flags)
+{
+	return 0;
+}
+#else
+# define dummy_get_unmapped_area NULL
+#endif
+
 /*
  *  Register section
  */
@@ -3401,6 +3412,7 @@ const struct file_operations snd_pcm_f_ops[2] = {
 		.compat_ioctl = 	snd_pcm_ioctl_compat,
 		.mmap =			snd_pcm_mmap,
 		.fasync =		snd_pcm_fasync,
+		.get_unmapped_area =	dummy_get_unmapped_area,
 	},
 	{
 		.owner =		THIS_MODULE,
@@ -3413,5 +3425,6 @@ const struct file_operations snd_pcm_f_ops[2] = {
 		.compat_ioctl = 	snd_pcm_ioctl_compat,
 		.mmap =			snd_pcm_mmap,
 		.fasync =		snd_pcm_fasync,
+		.get_unmapped_area =	dummy_get_unmapped_area,
 	}
 };