On Fri, 18 Mar 2011, Daniele Capuano wrote: > A little update. > It seems that the gadget itself has a strange behavior: I start > monitoring the usb transfers using usbmon. > My setup has remained the same, but NUM_ISO_PACKETS is 32. I also > tryed, as Hans suggested, to submit two urbs in order to achieve > double buffering, but nothing changed. > I attach a little view of the usbmon output. As you can see, the first > packet (second line) is received correctly, even though 1024 bytes are > received while a packet of 512 bytes was requested by the host. After No. The host requested 32 packets of 512 bytes each. 32 packets were received, but the only first two contained 512 bytes of data; the others all contained 0 bytes. BTW, that submission has a buffer-overrun bug. All the iso_frame_desc[n].offset values after the first lie beyond the end of the transfer buffer. You need to make sure that iso_in->iso_in_buffer is large enough to hold all NUM_ISO_PACKETS worth of data. Maybe this means you should set iso_in->maxpacket to 512, set iso_in->iso_in_buffer to iso_in->maxpacket * NUM_ISO_PACKETS, set urb->iso_frame_desc[i].offset to i * iso_in->maxpacket, and set urb->iso_frame_desc[i].length to iso_in->maxpacket. > such receipt, nothing more is received. > From the gadget, I monitored the callback calls, and I noticed that > the callback is continuously called, even before the host submit the > first urb. That sounds like a bug in the gadget's device controller driver. The callback shouldn't be called until the data transfer is completed, which can't happen until the host asks for it. I don't know the state of support for isochronous transfers using OMAP3550 in 2.6.32.. > Maybe this means that zero-length packets are sent all the > time before the host's first request. But what about the strange > behavior after the host's requests? A first data buffer is sent, but > then nothing more... it's seems quite strange to me... > > Thanks in advance for any idea... > Daniele > > --------USBMON OUTPUT------------ > f63bb000 2632500048 S Zi:5:009:2 -115:8:0 32 -18:0:512 -18:512:512 > -18:1024:512 -18:1536:512 -18:2048:512 512 < > f63bb000 2632540517 C Zi:5:009:2 0:8:8112:0 32 0:0:512 0:512:512 > 0:1024:0 0:1536:0 0:2048:0 1024 = bafcc8fc d0fcc4fc ccfcc1fc d1fcccfc > c8fcc1fc cafcbbfc c1fcc6fc c7fcd9fc Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
