[spice-gtk PATCH v3] Avoid compression of isochronous devices

[Snir Sheriber <ssheribe@xxxxxxxxxx>]

Device is considered isochronous if one of its endpoints is
defined as isochronous transfer, in that case data transfer
over the usbredir channel will not be compressed
(it is assumed that there is a strong correlation between
isochronous devices and devices which their data is usually
compressed)

E.g.
Camera/mic device will usually be recognised as isochronous
while storage devices won't
---
 src/channel-usbredir.c        |  9 +++++++++
 src/usb-device-manager-priv.h |  1 +
 src/usb-device-manager.c      | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/src/channel-usbredir.c b/src/channel-usbredir.c
index dd17e6c..2d025f5 100644
--- a/src/channel-usbredir.c
+++ b/src/channel-usbredir.c
@@ -544,6 +544,11 @@ void spice_usbredir_channel_disconnect_device_async(SpiceUsbredirChannel *channe
     g_object_unref(task);
 }
 
+static SpiceUsbDevice *spice_usbredir_channel_get_spice_usb_device(SpiceUsbredirChannel *channel)
+{
+    return channel->priv->spice_device;
+}
+
 G_GNUC_INTERNAL
 libusb_device *spice_usbredir_channel_get_device(SpiceUsbredirChannel *channel)
 {
@@ -673,6 +678,10 @@ static int try_write_compress_LZ4(SpiceUsbredirChannel *channel, uint8_t *data,
         /* No server compression capability - data will not be compressed */
         return FALSE;
     }
+    if(spice_usb_device_is_isochronous(spice_usbredir_channel_get_spice_usb_device(channel))) {
+        /* Don't compress - one of the device endpoints is isochronous */
+        return FALSE;
+    }
     bound = LZ4_compressBound(count);
     if (bound == 0) {
         /* Invalid bound - data will not be compressed */
diff --git a/src/usb-device-manager-priv.h b/src/usb-device-manager-priv.h
index b6fa9c9..83884d7 100644
--- a/src/usb-device-manager-priv.h
+++ b/src/usb-device-manager-priv.h
@@ -40,6 +40,7 @@ guint8 spice_usb_device_get_busnum(const SpiceUsbDevice *device);
 guint8 spice_usb_device_get_devaddr(const SpiceUsbDevice *device);
 guint16 spice_usb_device_get_vid(const SpiceUsbDevice *device);
 guint16 spice_usb_device_get_pid(const SpiceUsbDevice *device);
+gboolean spice_usb_device_is_isochronous(const SpiceUsbDevice *device);
 
 #endif
 
diff --git a/src/usb-device-manager.c b/src/usb-device-manager.c
index f076967..f117683 100644
--- a/src/usb-device-manager.c
+++ b/src/usb-device-manager.c
@@ -153,6 +153,7 @@ typedef struct _SpiceUsbDeviceInfo {
     guint8  devaddr;
     guint16 vid;
     guint16 pid;
+    gboolean isochronous;
 #ifdef G_OS_WIN32
     guint8  state;
 #else
@@ -2017,6 +2018,29 @@ gchar *spice_usb_device_get_description(SpiceUsbDevice *device, const gchar *for
 
 
 #ifdef USE_USBREDIR
+static gboolean probe_isochronous_endpoint(libusb_device *libdev) {
+    struct libusb_config_descriptor * conf_desc;
+    gboolean isoc_found = FALSE;
+    gint i,j,k;
+
+    g_return_val_if_fail(libdev != NULL, FALSE);
+    g_return_val_if_fail(!libusb_get_active_config_descriptor(libdev, &conf_desc), FALSE);
+
+    for(i = 0; !isoc_found && i < conf_desc->bNumInterfaces; i++) {
+        for(j = 0; !isoc_found && j < conf_desc->interface[i].num_altsetting; j++) {
+            for(k = 0; !isoc_found && k < conf_desc->interface[i].altsetting[j].bNumEndpoints;k++) {
+                gint attributes = conf_desc->interface[i].altsetting[j].endpoint[k].bmAttributes;
+                gint type = attributes & LIBUSB_TRANSFER_TYPE_MASK;
+                if (type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS)
+                    isoc_found = TRUE;
+            }
+        }
+    }
+
+    libusb_free_config_descriptor(conf_desc);
+    return isoc_found;
+}
+
 /*
  * SpiceUsbDeviceInfo
  */
@@ -2042,6 +2066,7 @@ static SpiceUsbDeviceInfo *spice_usb_device_new(libusb_device *libdev)
     info->vid = vid;
     info->pid = pid;
     info->ref = 1;
+    info->isochronous = probe_isochronous_endpoint(libdev);
 #ifndef G_OS_WIN32
     info->libdev = libusb_ref_device(libdev);
 #endif
@@ -2085,6 +2110,15 @@ guint16 spice_usb_device_get_pid(const SpiceUsbDevice *device)
     return info->pid;
 }
 
+gboolean spice_usb_device_is_isochronous(const SpiceUsbDevice *device)
+{
+    const SpiceUsbDeviceInfo *info = (const SpiceUsbDeviceInfo *)device;
+
+    g_return_val_if_fail(info != NULL, 0);
+
+    return info->isochronous;
+}
+
 #ifdef G_OS_WIN32
 void spice_usb_device_set_state(SpiceUsbDevice *device, guint8 state)
 {
-- 
2.5.5

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