On Tue, 9 Apr 2013, victor yeo wrote:
> Hi,
>
> > Earlier, you complained that your gadget was able to read the boot
> > sector but not the MBR! :-)
> >
> > How do you know the reads were sending all zeros? The usbmon output
> > shows only the first 32 bytes of each transfer, and the gadget
> > debugging output doesn't show the data for READ or WRITE commands at
> > all.
> >
> > What makes you think the gadget isn't reading the boot sector? What is
> > the boot sector's LBA (logical block address)?
>
> Earlier, i used file=/dev/mmcblk0p1. Now i use
> file=/mnt/sd/backing_file. This backing_file is a dummy file system
> that i created. I attached two jpeg files. One show the MBR and Boot
> Sector of the backing_file. Another shows the usbmon of the Linux Host
Why did you send jpeg files? Plain text files are a lot easier to work
with. Now I can't copy and paste the lines from your files into this
email message. :-(
> PC. I also attached the udc log which shows the MBR and Boot Sector
> content which are read from the backing_file.
The UDC log indicates that the MBR and boot sectors were read
correctly.
> From the usbmon jpeg,
> that first SCSI_READ_10 command got a overflow error, the second
> SCSI_READ_10 command got a connection reset error. Is the overflow
> error occurred because the host PC cannot handle the data returned
> from the gadget device?
The usbmon log shows that the host sent the gadget a READ(10) command
for 8 sectors, which 4096 bytes. It then requested a 4096-byte
transfer on the bulk-in endpoint, expecting the gadget to reply with
eight packets, each containing 512 bytes (because the bulk-in
wMaxPacketSize is 512).
But the gadget did not reply correctly. The UDC sent a data packet
containing only 256 bytes, instead of 512 bytes. The overflow occurred
when it sent a second data packet, again containing the wrong number of
bytes.
> > Call the gadget driver's ->reset handler. If the ->reset pointer is
> > NULL, call the ->disconnect handler instead. See the code in
> > net2280.c's handle_stat1_irqs() as an example.
> >
> > Alan Stern
> >
>
> i read the net2280.c code. Is it the usb_reset() function, called by
> stop_activity()? I am sorry if i understand incorrectly.
No, it is the handle_stat1_irqs() function, as I wrote above. In
particular, this part of the code, which handles both disconnects and
resets:
if (disconnect || reset) {
stop_activity(dev, dev->driver);
ep0_start(dev);
spin_unlock(&dev->lock);
if (reset && dev->driver->reset)
(dev->driver->reset)(&dev->gadget);
else
(dev->driver->disconnect)(&dev->gadget);
spin_lock(&dev->lock);
return;
}
Alan Stern
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