[ALSA] pcm core: add prealloc_max file to substream directory to show maximum DMA size

Users ask us many times about the maximum DMA size for PCM devices. This
file gives them a hint in KB.

Signed-off-by: Jaroslav Kysela <perex@suse.cz>

2 files changed, 24 insertions, 0 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 016c41893b06..ec006ed8cd59 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -384,6 +384,7 @@ struct snd_pcm_substream {
         struct snd_info_entry *proc_sw_params_entry;
         struct snd_info_entry *proc_status_entry;
         struct snd_info_entry *proc_prealloc_entry;
+        struct snd_info_entry *proc_prealloc_max_entry;
 #endif
         /* misc flags */
         unsigned int hw_opened: 1;
diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index be030cb4d373..95b1b2f0b1e2 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -101,6 +101,8 @@ int snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream)
 {
         snd_pcm_lib_preallocate_dma_free(substream);
 #ifdef CONFIG_SND_VERBOSE_PROCFS
+        snd_info_free_entry(substream->proc_prealloc_max_entry);
+        substream->proc_prealloc_max_entry = NULL;
         snd_info_free_entry(substream->proc_prealloc_entry);
         substream->proc_prealloc_entry = NULL;
 #endif
@@ -142,6 +144,18 @@ static void snd_pcm_lib_preallocate_proc_read(struct snd_info_entry *entry,
 }
 
 /*
+ * read callback for prealloc_max proc file
+ *
+ * prints the maximum allowed size in kB.
+ */
+static void snd_pcm_lib_preallocate_max_proc_read(struct snd_info_entry *entry,
+                                                  struct snd_info_buffer *buffer)
+{
+        struct snd_pcm_substream *substream = entry->private_data;
+        snd_iprintf(buffer, "%lu\n", (unsigned long) substream->dma_max / 1024);
+}
+
+/*
  * write callback for prealloc proc file
  *
  * accepts the preallocation size in kB.
@@ -203,6 +217,15 @@ static inline void preallocate_info_init(struct snd_pcm_substream *substream)
                 }
         }
         substream->proc_prealloc_entry = entry;
+        if ((entry = snd_info_create_card_entry(substream->pcm->card, "prealloc_max", substream->proc_root)) != NULL) {
+                entry->c.text.read = snd_pcm_lib_preallocate_max_proc_read;
+                entry->private_data = substream;
+                if (snd_info_register(entry) < 0) {
+                        snd_info_free_entry(entry);
+                        entry = NULL;
+                }
+        }
+        substream->proc_prealloc_max_entry = entry;
 }
 
 #else /* !CONFIG_SND_VERBOSE_PROCFS */