On Mon, 16 Feb 2009, Stanislaw Gruszka wrote: > Hello. > > I'm trying to use g_file_storage gadget on my embedded Atmel board and have > some troubles. It take _very_ long time to discovery device due to USB interface > resets which happen because of residue miscouting for MODE_SENSE command. No, that's not why the resets happen. The residue is not miscounted. > Below are debugging mesages in configuration where USB host is connected to USB > device on the same machine (USB cable loop). > > Whats happen? > - SCSI host driver set MODE SENSE command length to 192 > - device return 16 bytes of mode pages and set internal residue to 176, > - host does not check residue and try to get command status > - device halt bulk in endpoint > - host reset device You left out a few steps, but the details don't matter. > This sequence is repeated few times (SD_MAX_RETRIES times probably). > > I'm trying to fix the issue and currently wrote a workaround which looks > works quite well, but I did not test it for other transports than BBB: > > diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c > index b10fa31..0a77ba8 100644 > --- a/drivers/usb/gadget/file_storage.c > +++ b/drivers/usb/gadget/file_storage.c > @@ -2269,6 +2269,7 @@ static int do_mode_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh) > buf0[0] = len - 1; > else > put_be16(buf0, len - 2); > + fsg->residue = fsg->usb_amount_left = len; > return len; > } This patch is incorrect. len is the amount of data sent, not the residue. If you look at the end of do_scsi_command(), you'll see where the code calculates the correct residue. > Maybe this is not only problem with MODE SENSE command but with all commands > that have allocation length field and file_storage gadget driver BBB transport > return less data. > > Problem also happens in older kernels, I tried 2.6.27 and 2.6.24 - they have this issue. > Please let me know if have more info or any other help to fix. The problem is in the Atmel hardware; it's not capable of halting a bulk endpoint correctly. You need to invoke g_file_storage with the "stall=no" parameter. 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
