HDA driver: use optional settings file

Patch by Pete Goodeve, ticket #9134.
(Removed play_sample_rate and record_sample_rate as suggested in
patch review, adjusted hda.settings accordingly.)

Tune buffer size and buffer count with an optional settings file
/boot/home/config/settings/kernel/drivers/hda.settings. Same as
it's done for the auich driver.

Pete:
> I [...] request 4 buffers of 1024 frames, I get a nice 13-14ms latency.

Change-Id: I3c1c64375d22b525afb970d5e8379b22b8514438
Reviewed-on: https://review.haiku-os.org/521
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

src/add-ons/kernel/drivers/audio/hda/device.cpp

@@ -35,6 +35,10 @@ hda_open(const char* name, uint32 flags, void** cookie)
 	atomic_add(&controller->opened, 1);
 
 	*cookie = controller;
+
+	// optional user-settable buffer frames and count
+	get_settings_from_file();
+
 	return B_OK;
 }
 

src/add-ons/kernel/drivers/audio/hda/driver.h

@@ -365,6 +365,7 @@ void hda_codec_delete(hda_codec* codec);
 
 /* hda_multi_audio.c */
 status_t multi_audio_control(void* cookie, uint32 op, void* arg, size_t length);
+void get_settings_from_file();
 
 /* hda_controller.c: Basic controller support */
 status_t hda_hw_init(hda_controller* controller);

src/add-ons/kernel/drivers/audio/hda/hda.settings

@@ -0,0 +1,24 @@
+# Settings file for the HDA driver
+#
+#  This file should be moved to the directory
+#  ~/config/settings/kernel/drivers/
+#  Uncomment and edit any of the setting lines you wish to set.
+#  The values shown are just the defaults.
+#  Don't uncomment any that you don't need to differ from the default.
+
+#  Remember that latency will probably be at least
+#   2*buffer_frames/sample_rate
+#  For real time audio, a buffer of 1024 frames at 192000
+#  should be good (<15ms).
+#  You will need more buffers if they're small.
+#  e.g.:
+#     play_buffer_frames	1024
+#     play_buffer_count	4
+
+###########################################################
+
+# play_buffer_frames	10240
+# play_buffer_count	2
+
+# record_buffer_frames	10240
+# record_buffer_count	2

src/add-ons/kernel/drivers/audio/hda/hda_multi_audio.cpp

@@ -8,6 +8,8 @@
  */
 
 
+#include <driver_settings.h>
+
 #include "hmulti_audio.h"
 #include "driver.h"
 
@@ -71,6 +73,66 @@ format2size(uint32 format)
 }
 
 
+#define HDA_SETTINGS "hda.settings"
+
+static struct {
+	int32 play_buffer_frames;
+	int32 play_buffer_count;
+	int32 record_buffer_frames;
+	int32 record_buffer_count;
+} requested_settings;
+
+
+void
+get_settings_from_file()
+{
+	const char *item;
+	char       *end;
+	uint32      value;
+
+	memset(&requested_settings, 0, sizeof(requested_settings));
+	dprintf("looking for settings file\n");
+
+	void *settings_handle = load_driver_settings(HDA_SETTINGS);
+	if (settings_handle == NULL)
+		return;
+
+	item = get_driver_parameter (settings_handle, "play_buffer_frames", NULL,
+		NULL);
+	if (item) {
+		value = strtoul (item, &end, 0);
+		if (*end == '\0')
+			requested_settings.play_buffer_frames = value;
+		}
+
+	item = get_driver_parameter (settings_handle, "play_buffer_count", NULL,
+		NULL);
+	if (item) {
+		value = strtoul (item, &end, 0);
+		if (*end == '\0')
+			requested_settings.play_buffer_count = value;
+	}
+
+	item = get_driver_parameter (settings_handle, "record_buffer_frames", NULL,
+		NULL);
+	if (item) {
+		value = strtoul (item, &end, 0);
+		if (*end == '\0')
+			requested_settings.record_buffer_frames = value;
+	}
+
+	item = get_driver_parameter (settings_handle, "record_buffer_count", NULL,
+		NULL);
+	if (item) {
+		value = strtoul (item, &end, 0);
+		if (*end == '\0')
+			requested_settings.record_buffer_count = value;
+	}
+
+	unload_driver_settings(settings_handle);
+}
+
+
 static status_t
 get_description(hda_audio_group* audioGroup, multi_description* data)
 {
@@ -890,6 +952,18 @@ default_buffer_length_for_rate(uint32 rate)
 static status_t
 get_buffers(hda_audio_group* audioGroup, multi_buffer_list* data)
 {
+	if (requested_settings.play_buffer_frames != 0)
+		data->request_playback_buffer_size = requested_settings.play_buffer_frames;
+
+	if (requested_settings.play_buffer_count != 0)
+		data->request_playback_buffers = requested_settings.play_buffer_count;
+
+	if (requested_settings.record_buffer_frames != 0)
+		data->request_record_buffer_size = requested_settings.record_buffer_frames;
+
+	if (requested_settings.record_buffer_count != 0)
+		data->request_record_buffers = requested_settings.record_buffer_count;
+
 	TRACE("playback: %" B_PRId32 " buffers, %" B_PRId32 " channels, %" B_PRIu32
 		" samples\n", data->request_playback_buffers,
 		data->request_playback_channels, data->request_playback_buffer_size);