usb: gadget: f_mass_storage: make sysfs interface optional

When configfs is in place, the luns will not be represented in sysfs,
so there will be no struct device associated with a lun.
In order to maintain compatibility and allow configfs adoption
sysfs is made optional in this patch.

As a consequence some debug macros need to be adjusted. Two new
fields are added to struct fsg_lun: name and name_pfx.
The "name" is for storing a string which is presented to the user
instead of the dev_name. The "name_pfx", if non-NULL, is prepended
to the "name" at printing time.

The name_pfx is for a future lun.0, which will be a default group in
mass_storage.<name>. By design at USB function configfs group's creation
time its name is not known (but instead set a bit later in
drivers/usb/gadget/configfs.c:function_make) and it is this name that
serves the purpose of the said name prefix. So instead of copying
a yet-unknown string a pointer to it is stored in struct fsg_lun.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_mass_storage.c

@@ -299,6 +299,7 @@ struct fsg_common {
 	unsigned int		short_packet_received:1;
 	unsigned int		bad_lun_okay:1;
 	unsigned int		running:1;
+	unsigned int		sysfs:1;
 
 	int			thread_wakeup_needed;
 	struct completion	thread_notifier;
@@ -2642,6 +2643,11 @@ static inline int fsg_num_buffers_validate(unsigned int fsg_num_buffers)
 	return -EINVAL;
 }
 
+void fsg_common_set_sysfs(struct fsg_common *common, bool sysfs)
+{
+	common->sysfs = sysfs;
+}
+
 static void _fsg_common_free_buffers(struct fsg_buffhd *buffhds, unsigned n)
 {
 	if (buffhds) {
@@ -2654,6 +2660,34 @@ static void _fsg_common_free_buffers(struct fsg_buffhd *buffhds, unsigned n)
 	}
 }
 
+static inline void fsg_common_remove_sysfs(struct fsg_lun *lun)
+{
+	device_remove_file(&lun->dev, &dev_attr_nofua);
+	/*
+	 * device_remove_file() =>
+	 *
+	 * here the attr (e.g. dev_attr_ro) is only used to be passed to:
+	 *
+	 *	sysfs_remove_file() =>
+	 *
+	 *	here e.g. both dev_attr_ro_cdrom and dev_attr_ro are in
+	 *	the same namespace and
+	 *	from here only attr->name is passed to:
+	 *
+	 *		sysfs_hash_and_remove()
+	 *
+	 *		attr->name is the same for dev_attr_ro_cdrom and
+	 *		dev_attr_ro
+	 *		attr->name is the same for dev_attr_file and
+	 *		dev_attr_file_nonremovable
+	 *
+	 * so we don't differentiate between removing e.g. dev_attr_ro_cdrom
+	 * and dev_attr_ro
+	 */
+	device_remove_file(&lun->dev, &dev_attr_ro);
+	device_remove_file(&lun->dev, &dev_attr_file);
+}
+
 struct fsg_common *fsg_common_init(struct fsg_common *common,
 				   struct usb_composite_dev *cdev,
 				   struct fsg_config *cfg)
@@ -2687,6 +2721,8 @@ struct fsg_common *fsg_common_init(struct fsg_common *common,
 		memset(common, 0, sizeof *common);
 		common->free_storage_on_release = 0;
 	}
+	fsg_common_set_sysfs(common, true);
+	common->state = FSG_STATE_IDLE;
 
 	common->fsg_num_buffers = cfg->fsg_num_buffers;
 	common->buffhds = kcalloc(common->fsg_num_buffers,
@@ -2746,6 +2782,7 @@ struct fsg_common *fsg_common_init(struct fsg_common *common,
 		/* curlun->dev.driver = &fsg_driver.driver; XXX */
 		dev_set_drvdata(&curlun->dev, &common->filesem);
 		dev_set_name(&curlun->dev, "lun%d", i);
+		curlun->name = dev_name(&curlun->dev);
 
 		rc = device_register(&curlun->dev);
 		if (rc) {
@@ -2892,17 +2929,11 @@ static void fsg_common_release(struct kref *ref)
 			struct fsg_lun *lun = *lun_it;
 			if (!lun)
 				continue;
-			device_remove_file(&lun->dev, &dev_attr_nofua);
-			device_remove_file(&lun->dev,
-					   lun->cdrom
-					 ? &dev_attr_ro_cdrom
-					 : &dev_attr_ro);
-			device_remove_file(&lun->dev,
-					   lun->removable
-					 ? &dev_attr_file
-					 : &dev_attr_file_nonremovable);
+			if (common->sysfs)
+				fsg_common_remove_sysfs(lun);
 			fsg_lun_close(lun);
-			device_unregister(&lun->dev);
+			if (common->sysfs)
+				device_unregister(&lun->dev);
 			kfree(lun);
 		}
 

drivers/usb/gadget/f_mass_storage.h

@@ -102,6 +102,8 @@ struct fsg_common *fsg_common_init(struct fsg_common *common,
 				   struct usb_composite_dev *cdev,
 				   struct fsg_config *cfg);
 
+void fsg_common_set_sysfs(struct fsg_common *common, bool sysfs);
+
 void fsg_config_from_params(struct fsg_config *cfg,
 			    const struct fsg_module_parameters *params,
 			    unsigned int fsg_num_buffers);

drivers/usb/gadget/storage_common.h

@@ -17,10 +17,20 @@
 #define VLDBG(lun, fmt, args...) do { } while (0)
 #endif /* VERBOSE_DEBUG */
 
-#define LDBG(lun, fmt, args...)   dev_dbg(&(lun)->dev, fmt, ## args)
-#define LERROR(lun, fmt, args...) dev_err(&(lun)->dev, fmt, ## args)
-#define LWARN(lun, fmt, args...)  dev_warn(&(lun)->dev, fmt, ## args)
-#define LINFO(lun, fmt, args...)  dev_info(&(lun)->dev, fmt, ## args)
+#define _LMSG(func, lun, fmt, args...)					\
+	do {								\
+		if ((lun)->name_pfx && *(lun)->name_pfx)		\
+			func("%s/%s: " fmt, *(lun)->name_pfx,		\
+				 (lun)->name, ## args);			\
+		else							\
+			func("%s: " fmt, (lun)->name, ## args);		\
+	} while (0)
+
+#define LDBG(lun, fmt, args...)		_LMSG(pr_debug, lun, fmt, ## args)
+#define LERROR(lun, fmt, args...)	_LMSG(pr_err, lun, fmt, ## args)
+#define LWARN(lun, fmt, args...)	_LMSG(pr_warn, lun, fmt, ## args)
+#define LINFO(lun, fmt, args...)	_LMSG(pr_info, lun, fmt, ## args)
+
 
 #ifdef DUMP_MSGS
 
@@ -100,6 +110,8 @@ struct fsg_lun {
 						       of bound block device */
 	unsigned int	blksize; /* logical block size of bound block device */
 	struct device	dev;
+	const char	*name;		/* "lun.name" */
+	const char	**name_pfx;	/* "function.name" */
 };
 
 static inline bool fsg_lun_is_open(struct fsg_lun *curlun)