usb: gadget: mass_storage: added sysfs entry for cdrom to LUNsHEADkitkat

This patch adds a "cdrom" sysfs entry for each mass_storage LUN, just
like "ro" sysfs entry. This allows switching between USB and CD-ROM
emulation without reinserting the module or recompiling the kernel.

Change-Id: Idf83c74815b1ad370428ab9d3e5503d5f7bcd3b6

1 files changed, 37 insertions, 0 deletions

diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 3c57df4e18a..6788ce41aef 100644
--- a/drivers/usb/gadget/storage_common.c
+++ b/drivers/usb/gadget/storage_common.c
@@ -801,6 +801,14 @@ static ssize_t fsg_show_nofua(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "%u\n", curlun->nofua);
 }
 
+static ssize_t fsg_show_cdrom (struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
+
+	return sprintf(buf, "%d\n", curlun->cdrom);
+}
+
 #ifdef CONFIG_USB_MSC_PROFILING
 static ssize_t fsg_show_perf(struct device *dev, struct device_attribute *attr,
 			      char *buf)
@@ -956,3 +964,32 @@ 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_store_cdrom(struct device *dev, struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	ssize_t    rc;
+	struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
+	struct rw_semaphore  *filesem = dev_get_drvdata(dev);
+	unsigned  cdrom;
+
+	rc = kstrtouint(buf, 2, &cdrom);
+	if (rc)
+		return rc;
+
+	/*
+	 * Allow the cdrom status to change only while the
+	 * backing file is closed.
+	 */
+	down_read(filesem);
+	if (fsg_lun_is_open(curlun)) {
+		LDBG(curlun, "cdrom status change prevented\n");
+		rc = -EBUSY;
+	} else {
+		curlun->cdrom = cdrom;
+		LDBG(curlun, "cdrom status set to %d\n", curlun->cdrom);
+		rc = count;
+	}
+	up_read(filesem);
+	return rc;
+}