Hi Alan, This issue seems more related to the devices using SCSI protocol and the changes otherwise will be at more places giving the same end result. I think as the comment says over the command_abort function, intentional result change should only happen in case of timeout. Regards, Vishal -----Original Message----- From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] Sent: Tuesday, October 15, 2013 5:55 PM To: Ming Lei Cc: Vishal Annapurve; Linux Kernel Mailing List; linux-usb Subject: Re: [PATCH] usb-storage: scsiglue: Changing the command result On Tue, 15 Oct 2013, Ming Lei wrote: > 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. Instead of overriding the result code, a better way to do this would simply be to change the places where srb->result is currently set to DID_ABORT << 16. Just make it DID_TIME_OUT << 16 instead. 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
