Hi,
I am trying to check Isoch high bandwidth transfer with g_webcam.ko in
high-speed connection.
First I hacked webcam.c as follows to enable 640x480@30fps mode.
diff --git a/drivers/usb/gadget/legacy/webcam.c
b/drivers/usb/gadget/legacy/webcam.c
index 72c976b..9eb315f 100644
--- a/drivers/usb/gadget/legacy/webcam.c
+++ b/drivers/usb/gadget/legacy/webcam.c
@@ -191,15 +191,15 @@ static const struct UVC_FRAME_UNCOMPRESSED(3)
uvc_frame_yuv_360p = {
.bFrameIndex = 1,
.bmCapabilities = 0,
.wWidth = cpu_to_le16(640),
- .wHeight = cpu_to_le16(360),
+ .wHeight = cpu_to_le16(480),
.dwMinBitRate = cpu_to_le32(18432000),
.dwMaxBitRate = cpu_to_le32(55296000),
- .dwMaxVideoFrameBufferSize = cpu_to_le32(460800),
- .dwDefaultFrameInterval = cpu_to_le32(666666),
+ .dwMaxVideoFrameBufferSize = cpu_to_le32(614400),
+ .dwDefaultFrameInterval = cpu_to_le32(333333),
.bFrameIntervalType = 3,
- .dwFrameInterval[0] = cpu_to_le32(666666),
- .dwFrameInterval[1] = cpu_to_le32(1000000),
- .dwFrameInterval[2] = cpu_to_le32(5000000),
+ .dwFrameInterval[0] = cpu_to_le32(333333),
+ .dwFrameInterval[1] = cpu_to_le32(666666),
+ .dwFrameInterval[2] = cpu_to_le32(1000000),
};
then loaded g_webcam.ko as
# modprobe g_webcam streaming_maxpacket=3072
The endpoint descriptor showing on the host is
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x8d EP 13 IN
bmAttributes 5
Transfer Type Isochronous
Synch Type Asynchronous
Usage Type Data
wMaxPacketSize 0x1400 3x 1024 bytes
bInterval 1
However the usb bus trace shows only one transaction with 1024-bytes packet in
every SOF. The host only sends one IN packet in every SOF, I am expecting 2~3
1024-bytes transactions, since this would be required to transfer 640x480@30fps
YUV frames in high-speed.
DId I miss anything in the setup?
Thanks,
-Bin.
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