On Wed, Jan 04, 2023 at 06:27:50PM +0100, Petr Tesařík wrote:
> On Wed, 4 Jan 2023 12:04:22 -0500
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > At this point the host sends a Get-Device-Status request to the device
> > (not shown in the log).
> >
> > [...]
> >
> > The fact that the host is retrying means that the status request got an
> > error. Unfortunately the log message doesn't say sort of error
> > occurred.
>
> OK, I see. The URB indicates success, but there is no data:
>
> 45 0.432232 host 1.50.0 USB 64 GET STATUS Request
> 46 0.432659 1.50.0 host USB 64 GET STATUS Response
>
> Frame 46: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface usbmon1, id 0
> USB URB
> [Source: 1.50.0]
> [Destination: host]
> URB id: 0xffff98b4383c8d80
> URB type: URB_COMPLETE ('C')
> URB transfer type: URB_CONTROL (0x02)
> Endpoint: 0x80, Direction: IN
> Device: 50
> URB bus id: 1
> Device setup request: not relevant ('-')
> Data: present ('\0')
> URB sec: 1672851450
> URB usec: 569060
> URB status: Success (0)
> URB length [bytes]: 0
> Data length [bytes]: 0
> -------------------------^
> This should be 2, and the device should send a 16-bit status word. Hm.
>
> [Request in: 45]
> [Time from request: 0.000427000 seconds]
> Unused Setup Header
> Interval: 0
> Start frame: 0
> Copy of Transfer Flags: 0x00000200, Dir IN
> Number of ISO descriptors: 0
>
> While I do agree that the Samsung phone download mode USB stack
> implementation is crappy, multiple models and many users are affected. I
> wonder what would be a sensible workaround in heimdall and/or libusb...
>
> Setting a global module parameter does not sound great.
Another option would be to create a short udev script that would write
"on" to the power/control attribute file (thereby turning autosuspend
off) whenever it sees a new USB device with the vendor and product IDs
of your phone. That seems like a very practical solution.
Alan Stern
