USB: Mass storage gadget: Handle eject request

This patch adds handling of the "Start/Stop Unit" SCSI request
to simulate media ejection.

Signed-off-by: Fabien Chouteau <fabien.chouteau@barco.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 9dbe86d..c904aa3 100644 (file)
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -163,6 +163,10 @@
  * ro setting are not allowed when the medium is loaded or if CD-ROM
  * emulation is being used.
  *
+ * When a LUN receive an "eject" SCSI request (Start/Stop Unit),
+ * if the LUN is removable, the backing file is released to simulate
+ * ejection.
+ *
  *
  * This function is heavily based on "File-backed Storage Gadget" by
  * Alan Stern which in turn is heavily based on "Gadget Zero" by David
@@ -1384,12 +1388,50 @@ static int do_mode_sense(struct fsg_common *common, struct fsg_buffhd *bh)
 
 static int do_start_stop(struct fsg_common *common)
 {
-       if (!common->curlun) {
+       struct fsg_lun  *curlun = common->curlun;
+       int             loej, start;
+
+       if (!curlun) {
                return -EINVAL;
-       } else if (!common->curlun->removable) {
-               common->curlun->sense_data = SS_INVALID_COMMAND;
+       } else if (!curlun->removable) {
+               curlun->sense_data = SS_INVALID_COMMAND;
+               return -EINVAL;
+       }
+
+       loej = common->cmnd[4] & 0x02;
+       start = common->cmnd[4] & 0x01;
+
+       /* eject code from file_storage.c:do_start_stop() */
+
+       if ((common->cmnd[1] & ~0x01) != 0 ||     /* Mask away Immed */
+               (common->cmnd[4] & ~0x03) != 0) { /* Mask LoEj, Start */
+               curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
+
+       if (!start) {
+               /* Are we allowed to unload the media? */
+               if (curlun->prevent_medium_removal) {
+                       LDBG(curlun, "unload attempt prevented\n");
+                       curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
+                       return -EINVAL;
+               }
+               if (loej) {     /* Simulate an unload/eject */
+                       up_read(&common->filesem);
+                       down_write(&common->filesem);
+                       fsg_lun_close(curlun);
+                       up_write(&common->filesem);
+                       down_read(&common->filesem);
+               }
+       } else {
+
+               /* Our emulation doesn't support mounting; the medium is
+                * available for use as soon as it is loaded. */
+               if (!fsg_lun_is_open(curlun)) {
+                       curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
+                       return -EINVAL;
+               }
+       }
        return 0;
 }