[PATCH RESEND 2/2] Mass storage gadget: Handle eject request

[fabien . chouteau]

From: Fabien Chouteau <fabien.chouteau@xxxxxxxxx>

This patch adds handling of the "Start/Stop Unit" SCSI request to simulate media
ejection. A sysfs entry to get the "eject" state of a LUN is also added.

Signed-off-by: Fabien Chouteau <fabien.chouteau@xxxxxxxxx>
---
 drivers/usb/gadget/f_mass_storage.c |   57 +++++++++++++++++++++++++++++++++--
 drivers/usb/gadget/storage_common.c |   11 +++++++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index f4911c0..7b55435 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -163,6 +163,13 @@
  * 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.
+ * The "eject" state of a LUN is available in the "ejected" file of the
+ * LUN's sysfs directory (see above). The "eject" state is only updated
+ * by SCSI request, not by user 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
@@ -1385,12 +1392,51 @@ 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);
+			curlun->ejected = 1;
+			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;
 }
 
@@ -2641,6 +2687,7 @@ static int fsg_main_thread(void *common_)
 /* Write permission is checked per LUN in store_*() functions. */
 static DEVICE_ATTR(ro, 0644, fsg_show_ro, fsg_store_ro);
 static DEVICE_ATTR(file, 0644, fsg_show_file, fsg_store_file);
+static DEVICE_ATTR(ejected, 0444, fsg_show_ejected, NULL);
 
 
 /****************************** FSG COMMON ******************************/
@@ -2747,6 +2794,9 @@ static struct fsg_common *fsg_common_init(struct fsg_common *common,
 		rc = device_create_file(&curlun->dev, &dev_attr_file);
 		if (rc)
 			goto error_luns;
+		rc = device_create_file(&curlun->dev, &dev_attr_ejected);
+		if (rc)
+			goto error_luns;
 
 		if (lcfg->filename) {
 			rc = fsg_lun_open(curlun, lcfg->filename);
@@ -2887,6 +2937,7 @@ static void fsg_common_release(struct kref *ref)
 	for (; i; --i, ++lun) {
 		device_remove_file(&lun->dev, &dev_attr_ro);
 		device_remove_file(&lun->dev, &dev_attr_file);
+		device_remove_file(&lun->dev, &dev_attr_ejected);
 		fsg_lun_close(lun);
 		device_unregister(&lun->dev);
 	}
diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 868d8ee..16ccebd 100644
--- a/drivers/usb/gadget/storage_common.c
+++ b/drivers/usb/gadget/storage_common.c
@@ -267,6 +267,7 @@ struct fsg_lun {
 	unsigned int	removable:1;
 	unsigned int	cdrom:1;
 	unsigned int	prevent_medium_removal:1;
+	unsigned int	ejected:1;
 	unsigned int	registered:1;
 	unsigned int	info_valid:1;
 
@@ -625,6 +626,7 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
 	curlun->filp = filp;
 	curlun->file_length = size;
 	curlun->num_sectors = num_sectors;
+	curlun->ejected = 0;
 	LDBG(curlun, "open backing file: %s\n", filename);
 	rc = 0;
 
@@ -776,3 +778,12 @@ static ssize_t fsg_store_file(struct device *dev, struct device_attribute *attr,
 	up_write(filesem);
 	return (rc < 0 ? rc : count);
 }
+
+static ssize_t fsg_show_ejected(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
+
+	return sprintf(buf, "%d\n", curlun->ejected);
+}
+
-- 
1.7.0.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/