Handle snd_pcm_lib_mmap_vmalloc removal in 4.19

Add .mmap field back to pcm_ops for kernels older than 4.19.

Upstream-Status: Inappropriate

Signed-off-by: Scott Murray <scott.murray@konsulko.com>

diff --git a/aim-sound/sound.c b/aim-sound/sound.c
index 4b3329b..c0a26be 100644
--- a/aim-sound/sound.c
+++ b/aim-sound/sound.c
@@ -17,6 +17,7 @@
 #include <linux/printk.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/version.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
@@ -463,6 +464,9 @@ static const struct snd_pcm_ops pcm_ops = {
 	.trigger    = pcm_trigger,
 	.pointer    = pcm_pointer,
 	.page       = snd_pcm_lib_get_vmalloc_page,
+#if LINUX_VERSION_CODE <  KERNEL_VERSION(4,19,0)
+	.mmap       = snd_pcm_lib_mmap_vmalloc,
+#endif
 };
 
 static int split_arg_list(char *buf, char **card_name, u16 *ch_num,