mtd: rawnand: add hooks that may be called during nand_scan()

In order to remove the limitation that forbids dynamic allocation in
nand_scan_ident(), we must create a path that will be the same for all
controller drivers. The idea is to use nand_scan() instead of the widely
used nand_scan_ident()/nand_scan_tail() couple. In order to achieve
this, controller drivers will need to adjust some parameters between
these two functions depending on the NAND chip wired on them.

This takes the form of two new hooks (->{attach,detach}_chip()) that are
placed in a new nand_controller_ops structure, which is then attached
to the nand_controller object at driver initialization time.
->attach_chip() is called between nand_scan_ident() and
nand_scan_tail(), and ->detach_chip() is called in the error path of
nand_scan() and in nand_cleanup().

Note that some NAND controller drivers don't have a dedicated
nand_controller object and instead rely on the default/dummy one
embedded in nand_chip. If you're in this case and still want to
initialize the controller ops, you'll have to manipulate
chip->dummy_controller directly.

Last but not least, it's worth mentioning that we plan to move some of
the controller related hooks placed in nand_chip into
nand_controller_ops to make the separation between NAND chip and NAND
controller methods clearer.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/nand/raw/nand_base.c

@@ -6718,6 +6718,20 @@ err_free_buf:
 }
 EXPORT_SYMBOL(nand_scan_tail);
 
+static int nand_attach(struct nand_chip *chip)
+{
+	if (chip->controller->ops && chip->controller->ops->attach_chip)
+		return chip->controller->ops->attach_chip(chip);
+
+	return 0;
+}
+
+static void nand_detach(struct nand_chip *chip)
+{
+	if (chip->controller->ops && chip->controller->ops->detach_chip)
+		chip->controller->ops->detach_chip(chip);
+}
+
 /**
  * nand_scan_with_ids - [NAND Interface] Scan for the NAND device
  * @mtd: MTD device structure
@@ -6731,11 +6745,21 @@ EXPORT_SYMBOL(nand_scan_tail);
 int nand_scan_with_ids(struct mtd_info *mtd, int maxchips,
 		       struct nand_flash_dev *ids)
 {
+	struct nand_chip *chip = mtd_to_nand(mtd);
 	int ret;
 
 	ret = nand_scan_ident(mtd, maxchips, ids);
-	if (!ret)
-		ret = nand_scan_tail(mtd);
+	if (ret)
+		return ret;
+
+	ret = nand_attach(chip);
+	if (ret)
+		return ret;
+
+	ret = nand_scan_tail(mtd);
+	if (ret)
+		nand_detach(chip);
+
 	return ret;
 }
 EXPORT_SYMBOL(nand_scan_with_ids);
@@ -6763,7 +6787,11 @@ void nand_cleanup(struct nand_chip *chip)
 
 	/* Free manufacturer priv data. */
 	nand_manufacturer_cleanup(chip);
+
+	/* Free controller specific allocations after chip identification */
+	nand_detach(chip);
 }
+
 EXPORT_SYMBOL_GPL(nand_cleanup);
 
 /**

include/linux/mtd/rawnand.h

@@ -509,6 +509,25 @@ struct nand_id {
 	int len;
 };
 
+/**
+ * struct nand_controller_ops - Controller operations
+ *
+ * @attach_chip: this method is called after the NAND detection phase after
+ *		 flash ID and MTD fields such as erase size, page size and OOB
+ *		 size have been set up. ECC requirements are available if
+ *		 provided by the NAND chip or device tree. Typically used to
+ *		 choose the appropriate ECC configuration and allocate
+ *		 associated resources.
+ *		 This hook is optional.
+ * @detach_chip: free all resources allocated/claimed in
+ *		 nand_controller_ops->attach_chip().
+ *		 This hook is optional.
+ */
+struct nand_controller_ops {
+	int (*attach_chip)(struct nand_chip *chip);
+	void (*detach_chip)(struct nand_chip *chip);
+};
+
 /**
  * struct nand_controller - Structure used to describe a NAND controller
  *
@@ -517,11 +536,13 @@ struct nand_id {
  * @wq:			wait queue to sleep on if a NAND operation is in
  *			progress used instead of the per chip wait queue
  *			when a hw controller is available.
+ * @ops:		NAND controller operations.
  */
 struct nand_controller {
 	spinlock_t lock;
 	struct nand_chip *active;
 	wait_queue_head_t wq;
+	const struct nand_controller_ops *ops;
 };
 
 static inline void nand_controller_init(struct nand_controller *nfc)