Garmin: add MTP support

Create parallel helper functions that use libmtp to walk the file tree on the
device and to then read a specific file from the device into our dc_buffer.
MTP is not a file system, it's an object storage, that just happens to allow
object names and parent/child relationships between objects. As a result we
need to remember those file ids for MTP downloads (we could actually just not
remember the file names in that case).

The mtp_get_file_list function is rather complex as it includes both the
initial communication with the device and the code to walk the object tree and
then create the list of file.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

configure.ac

@@ -100,6 +100,19 @@ AS_IF([test "x$with_libusb" != "xno"], [
 	])
 ])
 
+# Checks for MTP support.
+AC_ARG_WITH([libmtp],
+	[AS_HELP_STRING([--without-libmtp],
+		[Build without the libmtp library])],
+	[], [with_libmtp=auto])
+AS_IF([test "x$with_libmtp" != "xno"], [
+	PKG_CHECK_MODULES([LIBMTP], [libmtp], [have_libmtp=yes], [have_libmtp=no])
+	AS_IF([test "x$have_libmtp" = "xyes"], [
+		AC_DEFINE([HAVE_LIBMTP], [1], [libmtp library])
+		DEPENDENCIES="$DEPENDENCIES libmtp"
+	])
+])
+
 # Checks for HIDAPI support.
 AC_ARG_WITH([hidapi],
 	[AS_HELP_STRING([--without-hidapi],

src/Makefile.am

@@ -1,9 +1,9 @@
 AM_CPPFLAGS = -I$(top_builddir)/include -I$(top_srcdir)/include
-AM_CFLAGS = $(LIBUSB_CFLAGS) $(HIDAPI_CFLAGS) $(BLUEZ_CFLAGS)
+AM_CFLAGS = $(LIBUSB_CFLAGS) $(LIBMTP_CFLAGS) $(HIDAPI_CFLAGS) $(BLUEZ_CFLAGS)
 
 lib_LTLIBRARIES = libdivecomputer.la
 
-libdivecomputer_la_LIBADD = $(LIBUSB_LIBS) $(HIDAPI_LIBS) $(BLUEZ_LIBS) -lm
+libdivecomputer_la_LIBADD = $(LIBUSB_LIBS) $(LIBMTP_LIBS) $(HIDAPI_LIBS) $(BLUEZ_LIBS) -lm
 libdivecomputer_la_LDFLAGS = \
 	-version-info $(DC_VERSION_LIBTOOL) \
 	-no-undefined \

src/descriptor.c

@@ -408,6 +408,7 @@ static const dc_descriptor_t g_descriptors[] = {
 	// Not merged upstream yet
 	/* Garmin */
 	{"Garmin", "Descent Mk1", DC_FAMILY_GARMIN, 2859, DC_TRANSPORT_USBSTORAGE, dc_filter_garmin},
+	{"Garmin", "Descent Mk2", DC_FAMILY_GARMIN, 0x4CBA, DC_TRANSPORT_USBSTORAGE, dc_filter_garmin},
 	/* Deepblu */
 	{"Deepblu", "Cosmiq+", DC_FAMILY_DEEPBLU, 0, DC_TRANSPORT_BLE, dc_filter_deepblu},
 	/* Oceans S1 */

src/garmin.c

@@ -35,10 +35,26 @@
 #include "device-private.h"
 #include "array.h"
 
+#ifdef HAVE_LIBMTP
+#include "libmtp.h"
+
+#define GARMIN_VENDOR 0x091E
+#define DESCENT_MK2   0x4CBA
+
+// deal with ancient libmpt found on older Linux distros
+#ifndef LIBMTP_FILES_AND_FOLDERS_ROOT
+#define LIBMTP_FILES_AND_FOLDERS_ROOT 0xffffffff
+#endif
+#endif
+
 typedef struct garmin_device_t {
 	dc_device_t base;
 	dc_iostream_t *iostream;
 	unsigned char fingerprint[FIT_NAME_SIZE];
+#ifdef HAVE_LIBMTP
+	unsigned char use_mtp;
+	LIBMTP_mtpdevice_t *mtp_device;
+#endif
 } garmin_device_t;
 
 static dc_status_t garmin_device_set_fingerprint (dc_device_t *abstract, const unsigned char data[], unsigned int size);
@@ -77,6 +93,12 @@ garmin_device_open (dc_device_t **out, dc_context_t *context, dc_iostream_t *ios
 	device->iostream = iostream;
 	memset(device->fingerprint, 0, sizeof(device->fingerprint));
 
+#ifdef HAVE_LIBMTP
+	// if this is a Descent Mk2/Mk2i, we have to use MTP to access its storage
+	device->use_mtp = (model == DESCENT_MK2);
+	DEBUG(context, "Found Garmin with model 0x%x which is a %s\n", model, (model == DESCENT_MK2 ? "Mk2i" : "Mk1"));
+#endif
+
 	*out = (dc_device_t *) device;
 
 	return DC_STATUS_SUCCESS;
@@ -104,13 +126,19 @@ garmin_device_close (dc_device_t *abstract)
 {
 	dc_status_t status = DC_STATUS_SUCCESS;
 	garmin_device_t *device = (garmin_device_t *) abstract;
-
+#ifdef HAVE_LIBMTP
+	if (device->use_mtp && device->mtp_device)
+		LIBMTP_Release_Device(device->mtp_device);
+#endif
 	return DC_STATUS_SUCCESS;
 }
 
 struct file_list {
 	int nr, allocated;
 	struct fit_name *array;
+#ifdef HAVE_LIBMTP
+	unsigned int *mtp_ids; // only used in the MTP case
+#endif
 };
 
 static int name_cmp(const void *a, const void *b)
@@ -124,29 +152,29 @@ static int name_cmp(const void *a, const void *b)
  *
  * Return number of files found.
 */
-static int get_file_list(dc_device_t *abstract, DIR *dir, struct file_list *files)
-{
-	struct dirent *de;
 
-	DEBUG (abstract->context, "Iterating over Garmin files");
-	while ((de = readdir(dir)) != NULL) {
-		int len = strlen(de->d_name);
-		struct fit_name *entry;
+static int
+check_filename(dc_device_t *abstract, const char *name)
+{
+	int len = strlen(name);
 	const char *explain = NULL;
 
-		DEBUG (abstract->context, "  %s", de->d_name);
+	DEBUG (abstract->context, "  %s", name);
 
 	if (len < 5)
 		explain = "name too short";
 	if (len >= FIT_NAME_SIZE)
 		explain = "name too long";
-		if (strncasecmp(de->d_name + len - 4, ".FIT", 4))
+	if (strncasecmp(name + len - 4, ".FIT", 4))
 		explain = "name lacks FIT suffix";
 
-		DEBUG (abstract->context, "  %s - %s", de->d_name, explain ? explain : "adding to list");
-		if (explain)
-			continue;
+	DEBUG (abstract->context, "  %s - %s", name, explain ? explain : "adding to list");
+	return explain == NULL;
+}
 
+static dc_status_t
+make_space(struct file_list *files, unsigned char is_mtp)
+{
 	if (files->nr == files->allocated) {
 		struct fit_name *array;
 		int n = 3*(files->allocated + 8)/2;
@@ -156,20 +184,53 @@ static int get_file_list(dc_device_t *abstract, DIR *dir, struct file_list *file
 		array = realloc(files->array, new_size);
 		if (!array)
 			return DC_STATUS_NOMEMORY;
-
+#ifdef HAVE_LIBMTP
+		if (is_mtp) {
+			unsigned int *mtp_ids;
+			new_size = n * sizeof(unsigned int);
+			mtp_ids = realloc(files->mtp_ids, new_size);
+			if (!mtp_ids)
+				return DC_STATUS_NOMEMORY;
+			files->mtp_ids = mtp_ids;
+		}
+#else
+		(void)is_mtp;
+#endif
 		files->array = array;
 		files->allocated = n;
 	}
+	return DC_STATUS_SUCCESS;
 
+}
+
+static void
+add_name(struct file_list *files, const char *name)
+{
 	/*
 	 * NOTE! This depends on the zero-padding that strncpy does.
 	 *
 	 * strncpy() doesn't just limit the size of the copy, it
 	 * will zero-pad the end of the result buffer.
 	 */
-		entry = files->array + files->nr++;
-		strncpy(entry->name, de->d_name, FIT_NAME_SIZE);
+	struct fit_name *entry = files->array + files->nr++;
+	strncpy(entry->name, name, FIT_NAME_SIZE);
 	entry->name[FIT_NAME_SIZE] = 0; // ensure it's null-terminated
+}
+
+static dc_status_t
+get_file_list(dc_device_t *abstract, DIR *dir, struct file_list *files)
+{
+	struct dirent *de;
+
+	DEBUG (abstract->context, "Iterating over Garmin files");
+	while ((de = readdir(dir)) != NULL) {
+		if (!check_filename(abstract, de->d_name))
+			continue;
+
+		dc_status_t rc = make_space(files, 0);
+		if (rc != DC_STATUS_SUCCESS)
+			return rc;
+		add_name(files, de->d_name);
 	}
 	DEBUG (abstract->context, "Found %d files", files->nr);
 
@@ -177,6 +238,117 @@ static int get_file_list(dc_device_t *abstract, DIR *dir, struct file_list *file
 	return DC_STATUS_SUCCESS;
 }
 
+#ifdef HAVE_LIBMTP
+static unsigned int
+mtp_get_folder_id(dc_device_t *abstract, LIBMTP_mtpdevice_t *device, LIBMTP_devicestorage_t *storage, const char *folder, unsigned int parent_id)
+{
+	DEBUG(abstract->context, "looking for folder %s under parent id %d", folder, parent_id);
+	// memory management is interesting here - we have to always walk the list returned and destroy them one by one
+	unsigned int folder_id = LIBMTP_FILES_AND_FOLDERS_ROOT;
+	LIBMTP_file_t* files = LIBMTP_Get_Files_And_Folders (device, storage->id, parent_id);
+	while (files != NULL) {
+		LIBMTP_file_t* mtp_file = files;
+		if (mtp_file->filename)
+			DEBUG(abstract->context, "looking at %s", mtp_file->filename);
+		if (mtp_file->filetype == LIBMTP_FILETYPE_FOLDER && mtp_file->filename && !strncasecmp(mtp_file->filename, folder, strlen(folder))) {
+			folder_id = mtp_file->item_id;
+		}
+		files = files->next;
+		LIBMTP_destroy_file_t(mtp_file);
+	}
+	return folder_id;
+}
+
+static dc_status_t
+mtp_get_file_list(dc_device_t *abstract, struct file_list *files)
+{
+	garmin_device_t *device = (garmin_device_t *)abstract;
+	LIBMTP_raw_device_t *rawdevices;
+	int numrawdevices;
+	int i;
+
+	LIBMTP_Init();
+	DEBUG(abstract->context, "Attempting to connect to mtp device");
+
+	switch (LIBMTP_Detect_Raw_Devices(&rawdevices, &numrawdevices)) {
+	case LIBMTP_ERROR_NO_DEVICE_ATTACHED:
+		DEBUG(abstract->context, "Garmin/mtp: no device found");
+		return DC_STATUS_NODEVICE;
+	case LIBMTP_ERROR_CONNECTING:
+		DEBUG(abstract->context, "Garmin/mtp: error connecting");
+		return DC_STATUS_NOACCESS;
+	case LIBMTP_ERROR_MEMORY_ALLOCATION:
+		DEBUG(abstract->context, "Garmin/mtp: memory allocation error");
+		return DC_STATUS_NOMEMORY;
+
+	case LIBMTP_ERROR_GENERAL: // Unknown general errors - that's bad
+	default:
+		DEBUG(abstract->context, "Garmin/mtp: unknown error");
+		return DC_STATUS_UNSUPPORTED;
+
+	case LIBMTP_ERROR_NONE:
+		DEBUG(abstract->context, "Garmin/mtp: successfully connected with %d raw devices", numrawdevices);
+	}
+
+	/* iterate through connected MTP devices */
+	for (i = 0; i < numrawdevices; i++) {
+		LIBMTP_devicestorage_t *storage;
+		char *devicename;
+		int ret;
+
+		// we only want to read from a Garmin Descent Mk2 device at this point
+		if (rawdevices[i].device_entry.vendor_id != GARMIN_VENDOR || rawdevices[i].device_entry.product_id != DESCENT_MK2) {
+			DEBUG(abstract->context, "Garmin/mtp: skipping raw device %04x/%04x",
+			      rawdevices[i].device_entry.vendor_id, rawdevices[i].device_entry.product_id);
+			continue;
+		}
+		device->mtp_device = LIBMTP_Open_Raw_Device_Uncached(&rawdevices[i]);
+		if (device->mtp_device == NULL) {
+			DEBUG(abstract->context, "Garmin/mtp: unable to open raw device %d", i);
+			continue;
+		}
+		DEBUG(abstract->context, "Garmin/mtp: succcessfully opened device");
+
+		LIBMTP_Dump_Errorstack(device->mtp_device);
+		LIBMTP_Clear_Errorstack(device->mtp_device);
+		for (storage = device->mtp_device->storage; storage != 0; storage = storage->next) {
+			DEBUG(abstract->context, "Garmin/mtp: looking at storage %d", storage->id);
+			unsigned int garmin_id = mtp_get_folder_id(abstract, device->mtp_device, storage, "Garmin", LIBMTP_FILES_AND_FOLDERS_ROOT);
+			DEBUG(abstract->context, "Garmin/mtp: garmin folder at file_id %d", garmin_id);
+						if (garmin_id == LIBMTP_FILES_AND_FOLDERS_ROOT)
+				continue; // this storage partition didn't have a Garmin folder
+			unsigned int activity_id = mtp_get_folder_id(abstract, device->mtp_device, storage, "Activity", garmin_id);
+			DEBUG(abstract->context, "Garmin/mtp: activity folder at file_id %d", activity_id);
+			if (activity_id == LIBMTP_FILES_AND_FOLDERS_ROOT)
+				continue; // no Activity folder
+
+			// now walk that folder to create our file_list
+			LIBMTP_file_t* activity_files = LIBMTP_Get_Files_And_Folders (device->mtp_device, storage->id, activity_id);
+			while (activity_files != NULL) {
+				LIBMTP_file_t* mtp_file = activity_files;
+				if (mtp_file->filetype != LIBMTP_FILETYPE_FOLDER && mtp_file->filename) {
+					if (check_filename(abstract, mtp_file->filename)) {
+						dc_status_t rc = make_space(files, 1);
+						if (rc != DC_STATUS_SUCCESS)
+							return rc;
+						add_name(files, mtp_file->filename);
+						files->mtp_ids[files->nr - 1] = mtp_file->item_id;
+					}
+				}
+				activity_files = activity_files->next;
+				LIBMTP_destroy_file_t(mtp_file);
+			}
+		}
+	}
+	free(rawdevices);
+	DEBUG (abstract->context, "Found %d files", files->nr);
+
+	qsort(files->array, files->nr, sizeof(struct fit_name), name_cmp);
+
+	return DC_STATUS_SUCCESS;
+}
+#endif /* HAVE_LIBMTP */
+
 #ifndef O_BINARY
 #define O_BINARY 0
 #endif
@@ -213,6 +385,37 @@ read_file(char *pathname, int pathlen, const char *name, dc_buffer_t *file)
 	return rc;
 }
 
+#ifdef HAVE_LIBMTP
+// MTP hands us the file data in chunks which we then just add to our data buffer
+static uint16_t
+mtp_put_func(void* params, void* priv, uint32_t sendlen, unsigned char *data, uint32_t *putlen)
+{
+	dc_buffer_t *file = (dc_buffer_t *)priv;
+	dc_buffer_append(file, data, sendlen);
+	if (putlen)
+		*putlen = sendlen;
+	return 0;
+}
+
+// read the file from the MTP device and store the content in the data buffer
+static dc_status_t
+mtp_read_file(garmin_device_t *device, unsigned int file_id, dc_buffer_t *file)
+{
+	dc_status_t rc = DC_STATUS_SUCCESS;
+	if (!device->mtp_device) {
+		DEBUG(device->base.context, "Garmin/mtp: cannot read file without MTP device");
+		return DC_STATUS_NODEVICE;
+	}
+	DEBUG(device->base.context, "Garmin/mtp: call Get_File_To_Handler");
+	if (LIBMTP_Get_File_To_Handler(device->mtp_device, file_id, &mtp_put_func, (void *) file, NULL, NULL) != 0) {
+		// show errors?
+		LIBMTP_Dump_Errorstack(device->mtp_device);
+		return DC_STATUS_IO;
+	}
+	return rc;
+}
+#endif /* HAVE_LIBMTP */
+
 static dc_status_t
 garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void *userdata)
 {
@@ -221,10 +424,17 @@ garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void
 	dc_parser_t *parser;
 	char pathname[PATH_MAX];
 	size_t pathlen;
-	struct file_list files = { 0, 0, NULL };
+	struct file_list files = {
+		0,     // nr
+		0,     // allocated
+		NULL,  // array of names
+#ifdef HAVE_LIBMTP
+		NULL   // array of file ids
+#endif
+	};
 	dc_buffer_t *file;
 	DIR *dir;
-	int rc;
+	dc_status_t rc;
 
 	// Read the directory name from the iostream
 	rc = dc_iostream_read(device->iostream, &pathname, sizeof(pathname)-1, &pathlen);
@@ -239,18 +449,30 @@ garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void
 		ERROR (abstract->context, "Invalid Garmin base directory '%s'", pathname);
 		return DC_STATUS_IO;
 	}
+	DEBUG (abstract->context, "Garmin base directory '%s'", pathname);
 
 	if (pathlen && pathname[pathlen-1] != '/')
 		pathname[pathlen++] = '/';
 	strcpy(pathname + pathlen, "Garmin/Activity");
 	pathlen += strlen("Garmin/Activity");
 
+#ifdef HAVE_LIBMTP
+	if (device->use_mtp) {
+		rc = mtp_get_file_list(abstract, &files);
+		DEBUG(abstract->context, "mtp_get_file_list rc %d with %d files", (int)rc, files.nr);
+		if (rc != DC_STATUS_SUCCESS || !files.nr) {
+			free(files.array);
+			free(files.mtp_ids);
+			return rc;
+		}
+	} else
+#endif
+	{ // slight coding style violation to deal with the non-MTP case
 		dir = opendir(pathname);
 		if (!dir) {
 			ERROR (abstract->context, "Failed to open directory '%s'.", pathname);
 			return DC_STATUS_IO;
 		}
-
 		// Get the list of FIT files
 		rc = get_file_list(abstract, dir, &files);
 		closedir(dir);
@@ -258,7 +480,8 @@ garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void
 			free(files.array);
 			return rc;
 		}
-
+	}
+	// We found at least one file
 	// Can we find the fingerprint entry?
 	for (int i = 0; i < files.nr; i++) {
 		const char *name = files.array[i].name;
@@ -271,7 +494,6 @@ garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void
 		DEBUG (abstract->context, "Ignoring '%s' and older", name);
 		break;
 	}
-
 	// Enable progress notifications.
 	dc_event_progress_t progress = EVENT_PROGRESS_INITIALIZER;
 	progress.maximum = files.nr;
@@ -306,8 +528,15 @@ garmin_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, void
 		// Reset the membuffer, read the data
 		dc_buffer_clear(file);
 		dc_buffer_append(file, name, FIT_NAME_SIZE);
-
+#ifdef HAVE_LIBMTP
+		if (device->use_mtp) {
+			DEBUG(abstract->context, "start reading file id %d", files.mtp_ids[i]);
+			status = mtp_read_file(device, files.mtp_ids[i], file);
+		} else
+#endif
+		{
 			status = read_file(pathname, pathlen, name, file);
+		}
 		if (status != DC_STATUS_SUCCESS)
 			break;
 

src/usb_storage.c

@@ -76,10 +76,14 @@ dc_usb_storage_open (dc_iostream_t **out, dc_context_t *context, const char *nam
 	if (out == NULL || name == NULL)
 		return DC_STATUS_INVALIDARGS;
 
+	if (*name == '\0') {
+		// that indicates an MTP device
+		INFO (context, "Open MTP device");
+	} else {
 		INFO (context, "Open: name=%s", name);
 		if (stat(name, &st) < 0 || !S_ISDIR(st.st_mode))
 			return DC_STATUS_NODEVICE;
-
+	}
 	// Allocate memory.
 	device = (dc_usbstorage_t *) dc_iostream_allocate (context, &dc_usbstorage_vtable, DC_TRANSPORT_USBSTORAGE);
 	if (device == NULL) {