Mark Knibbs 646a384317 storage: Fix bus scan and multi-LUN support for SCM eUSCSI devices
This patch does two things for SCM eUSCSI USB-SCSI converters:

1. SCM eUSCSI bridge devices are hard-wired to use SCSI ID 7. On connecting
the converter, access to that ID is attempted during the bus scan. Asking
the converter to issue INQUIRY commands to itself isn't very polite and
wastes time. Set this_id to 7 so __scsi_scan_target() skips it in the scan.

2. Enable multi-LUN support. eUSCSI devices don't support Get Max LUN
requests, returning an error (-32). [Different targets could have different
numbers of LUNs, so it wouldn't make sense to return a particular value in
response to Get Max LUN.]

usb_stor_scan_dwork() does this:
    /* For bulk-only devices, determine the max LUN value */
    if (us->protocol == USB_PR_BULK && !(us->fflags & US_FL_SINGLE_LUN)) {
            mutex_lock(&us->dev_mutex);
            us->max_lun = usb_stor_Bulk_max_lun(us);
            mutex_unlock(&us->dev_mutex);

It avoids calling usb_stor_Bulk_max_lun() if US_FL_SINGLE_LUN, but not for
US_FL_SCM_MULT_TARG. Since usb_stor_Bulk_max_lun() returns 0 in the error
case, us->max_lun was always set to 0.

[If the user doesn't want multi-LUN support (perhaps there are SCSI devices
which respond to commands on all LUNs?), the US_FL_SINGLE_LUN quirk can be
specified on the kernel command line.]

Signed-off-by: Mark Knibbs <markk@clara.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-24 17:22:38 -08:00
..
2014-11-10 12:10:24 +09:00
2013-09-26 16:25:21 -07:00
2014-09-25 17:05:12 +02:00

To understand all the Linux-USB framework, you'll use these resources:

    * This source code.  This is necessarily an evolving work, and
      includes kerneldoc that should help you get a current overview.
      ("make pdfdocs", and then look at "usb.pdf" for host side and
      "gadget.pdf" for peripheral side.)  Also, Documentation/usb has
      more information.

    * The USB 2.0 specification (from www.usb.org), with supplements
      such as those for USB OTG and the various device classes.
      The USB specification has a good overview chapter, and USB
      peripherals conform to the widely known "Chapter 9".

    * Chip specifications for USB controllers.  Examples include
      host controllers (on PCs, servers, and more); peripheral
      controllers (in devices with Linux firmware, like printers or
      cell phones); and hard-wired peripherals like Ethernet adapters.

    * Specifications for other protocols implemented by USB peripheral
      functions.  Some are vendor-specific; others are vendor-neutral
      but just standardized outside of the www.usb.org team.

Here is a list of what each subdirectory here is, and what is contained in
them.

core/		- This is for the core USB host code, including the
		  usbfs files and the hub class driver ("hub_wq").

host/		- This is for USB host controller drivers.  This
		  includes UHCI, OHCI, EHCI, and others that might
		  be used with more specialized "embedded" systems.

gadget/		- This is for USB peripheral controller drivers and
		  the various gadget drivers which talk to them.


Individual USB driver directories.  A new driver should be added to the
first subdirectory in the list below that it fits into.

image/		- This is for still image drivers, like scanners or
		  digital cameras.
../input/	- This is for any driver that uses the input subsystem,
		  like keyboard, mice, touchscreens, tablets, etc.
../media/	- This is for multimedia drivers, like video cameras,
		  radios, and any other drivers that talk to the v4l
		  subsystem.
../net/		- This is for network drivers.
serial/		- This is for USB to serial drivers.
storage/	- This is for USB mass-storage drivers.
class/		- This is for all USB device drivers that do not fit
		  into any of the above categories, and work for a range
		  of USB Class specified devices. 
misc/		- This is for all USB device drivers that do not fit
		  into any of the above categories.