mtd: Add a function to report when the MTD dev list has been updated

We need to parse mtdparts/mtids again everytime a device has been
added/removed from the MTD list, but there's currently no way to know
when such an update has been done.

Add an ->updated field to the idr struct that we set to true every time
a device is added/removed and expose a function returning the value
of this field and resetting it to false.
Signed-off-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Tested-by: NHeiko Schocher <hs@denx.de>

drivers/mtd/mtdcore.c

@@ -87,14 +87,17 @@ struct idr_layer {
 
 struct idr {
 	struct idr_layer id[MAX_IDR_ID];
+	bool updated;
 };
 
 #define DEFINE_IDR(name)	struct idr name;
 
 void idr_remove(struct idr *idp, int id)
 {
-	if (idp->id[id].used)
+	if (idp->id[id].used) {
 		idp->id[id].used = 0;
+		idp->updated = true;
+	}
 
 	return;
 }
@@ -134,6 +137,7 @@ int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask)
 		if (idl->used == 0) {
 			idl->used = 1;
 			idl->ptr = ptr;
+			idp->updated = true;
 			return i;
 		}
 		i++;
@@ -155,6 +159,16 @@ struct mtd_info *__mtd_next_device(int i)
 }
 EXPORT_SYMBOL_GPL(__mtd_next_device);
 
+bool mtd_dev_list_updated(void)
+{
+	if (mtd_idr.updated) {
+		mtd_idr.updated = false;
+		return true;
+	}
+
+	return false;
+}
+
 #ifndef __UBOOT__
 static LIST_HEAD(mtd_notifiers);
 

include/linux/mtd/mtd.h

@@ -581,6 +581,7 @@ int mtd_arg_off_size(int argc, char *const argv[], int *idx, loff_t *off,
 void mtd_get_len_incl_bad(struct mtd_info *mtd, uint64_t offset,
 			  const uint64_t length, uint64_t *len_incl_bad,
 			  int *truncated);
+bool mtd_dev_list_updated(void);
 
 /* drivers/mtd/mtd_uboot.c */
 int mtd_search_alternate_name(const char *mtdname, char *altname,