On Thu, Sep 26, 2013 at 7:35 PM, Vishal Annapurve <vannapurve@xxxxxxxxxx> wrote: > Hi, > > There was a recent commit in mainline for the scsi devices which do not > respond properly to medium access command: > > commit 18a4d0a22ed6c54b67af7718c305cd010f09ddf8 > > [SCSI] Handle disk devices which can not process medium access commands > We have experienced several devices which fail in a fashion we do not > currently handle gracefully in SCSI. After a failure these devices will > respond to the SCSI primary command set (INQUIRY, TEST UNIT READY, etc.) > but any command accessing the storage medium will time out. > > I came across a USB drive which showed similar problem and what I see is > usb storage is still not able to cope with such devices properly. > > The control flow downwards is like: > scsi_times_out --> Setting cmd->result as DID_TIME_OUT > scsi_error_handler > scsi_unjam_host > scsi_eh_abort_cmds > command_abort (sets US_FLIDX_TIMED_OUT for us->dflags > calls stop_transport, > and waits for) usb_stor_control_thread > (which is waiting for > transport > call to return inside > > usb_stor_invoke_transport) > both > usb_stor_control_thread and > > usb_stor_invoke_transport > check for us->dflags > timed_out bit and > set the result as > DID_ABORT > and signal completion > for command_abort > to complete > ...... > sd_eh_action > checks for cmd->result and finds out that it's DID_ABORT rather than > DID_TIME_OUT. > > This patch updates the command result to be TIME_OUT explicitly before > returning from command_abort in scsiglue.c. > > I would like to know if this patch can work out for such USB Storage > devices? What would be the better way to do the same? Looks your diagnose is correct, and patch should be doable, the only side effect is that previous returned DID_ABORT in srb->result is replaced with DID_TIME_OUT now. Another way is to implement .eh_timed_out callback to return different error for the two failure, but looks not a big deal. Thanks, -- Ming Lei -- 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
