Merge pull request #58 from amtep/master

Fix MTP compatibility with some android kernels

mts/transport/usb/descriptor.c

@@ -94,3 +94,11 @@ const struct mtp1strings_s mtp1strings = {
       MTP_STRING_DESCRIPTOR,
    },
 };
+
+const struct usb_functionfs_descs_head_incompatible mtp1descriptors_header_incompatible = {
+  .magic = cpu_to_le32(FUNCTIONFS_DESCRIPTORS_MAGIC),
+  .length = cpu_to_le32(sizeof(struct mtp1_descriptors_s_incompatible)),
+  .fs_count = 4,
+  .hs_count = 4,
+  .ss_count = 0
+};

mts/transport/usb/mtp1descriptors.h

@@ -17,14 +17,17 @@ static const char* in_file = "/dev/mtp/ep1";
 static const char* out_file = "/dev/mtp/ep2";
 static const char* interrupt_file = "/dev/mtp/ep3";
 
+struct mtp1_descs_s {
+   struct usb_interface_descriptor intf;
+   struct usb_endpoint_descriptor_no_audio mtp_ep_in;
+   struct usb_endpoint_descriptor_no_audio mtp_ep_out;
+   struct usb_endpoint_descriptor_no_audio mtp_ep_int;
+} __attribute__((packed));
+
 struct mtp1_descriptors_s {
    struct usb_functionfs_descs_head header;
-   struct {
-      struct usb_interface_descriptor intf;
-      struct usb_endpoint_descriptor_no_audio mtp_ep_in;
-      struct usb_endpoint_descriptor_no_audio mtp_ep_out;
-      struct usb_endpoint_descriptor_no_audio mtp_ep_int;
-   } __attribute__((packed)) fs_descs, hs_descs;
+   struct mtp1_descs_s fs_descs;
+   struct mtp1_descs_s hs_descs;
 } __attribute__((packed));
 
 extern const struct mtp1_descriptors_s mtp1descriptors;
@@ -39,4 +42,23 @@ struct mtp1strings_s {
 
 extern const struct mtp1strings_s mtp1strings;
 
+
+struct usb_functionfs_descs_head_incompatible {
+        __le32 magic;
+        __le32 length;
+        __le32 fs_count;
+        __le32 hs_count;
+       // The following field is added to the header in some
+       // android kernels, which breaks compatibility.
+        __le32 ss_count;
+} __attribute__((packed));
+
+struct mtp1_descriptors_s_incompatible {
+   struct usb_functionfs_descs_head_incompatible header;
+   struct mtp1_descs_s fs_descs;
+   struct mtp1_descs_s hs_descs;
+} __attribute__((packed));
+
+extern const struct usb_functionfs_descs_head_incompatible mtp1descriptors_header_incompatible;
+
 #endif

mts/transport/usb/mtptransporterusb.cpp

@@ -32,6 +32,7 @@
 #include <signal.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <fcntl.h>
@@ -72,6 +73,39 @@ MTPTransporterUSB::MTPTransporterUSB() : m_ioState(SUSPENDED), m_containerReadLe
         this, SLOT(handleDataReady()), Qt::QueuedConnection);
 }
 
+bool MTPTransporterUSB::writeMtpDescriptors()
+{
+    if (write(m_ctrlFd, &mtp1descriptors, sizeof mtp1descriptors) >= 0)
+        return true;
+
+    if (errno == EINVAL) {
+        MTP_LOG_WARNING("Kernel did not accept endpoint descriptors;"
+            " trying 'ss_count' workaround");
+        // Some android kernels changed the usb_functionfs_descs_head size
+        // by adding an ss_count member. Try it that way.
+        mtp1_descriptors_s_incompatible descs;
+        descs.header = mtp1descriptors_header_incompatible;
+        descs.fs_descs = mtp1descriptors.fs_descs;
+        descs.hs_descs = mtp1descriptors.hs_descs;
+        if (write(m_ctrlFd, &descs, sizeof descs) >= 0)
+            return true;
+    }
+
+    MTP_LOG_CRITICAL("Couldn't write descriptors to control endpoint file"
+        << control_file);
+    return false;
+}
+
+bool MTPTransporterUSB::writeMtpStrings()
+{
+    if (write(m_ctrlFd, &mtp1strings, sizeof(mtp1strings)) >= 0)
+        return true;
+
+    MTP_LOG_CRITICAL("Couldn't write strings to control endpoint file"
+        << control_file);
+    return false;
+}
+
 bool MTPTransporterUSB::activate()
 {
     MTP_LOG_CRITICAL("MTPTransporterUSB::activate");
@@ -84,23 +118,9 @@ bool MTPTransporterUSB::activate()
     }
     else
     {
-        if(-1 == write(m_ctrlFd, &mtp1descriptors, sizeof mtp1descriptors))
-        {
-            MTP_LOG_CRITICAL("Couldn't write descriptors to control endpoint file "
-                << control_file);
-        }
-        else
-        {
-            if(-1 == write(m_ctrlFd, &mtp1strings, sizeof(mtp1strings)))
-            {
-                MTP_LOG_CRITICAL("Couldn't write strings to control endpoint file "
-                    << control_file);
-            }
-            else
-            {
-                success = true;
-                MTP_LOG_INFO("mtp function set up");
-            }
+        if (writeMtpDescriptors() && writeMtpStrings()) {
+            success = true;
+            MTP_LOG_INFO("mtp function set up");
         }
     }
 

mts/transport/usb/mtptransporterusb.h

@@ -93,6 +93,8 @@ class MTPTransporterUSB : public MTPTransporter
 
     private:
         void processReceivedData();  // Helper function for handleDataReady()
+        bool writeMtpDescriptors();  // configure the USB endpoints for functionfs
+        bool writeMtpStrings();      // step 2 of functionfs configuration
 
         enum IOState{
             ACTIVE,