[RFC PATCH 3/3] mtd: rawnand: add hooks that may be called during nand_scan()

[Miquel Raynal <miquel.raynal@bootlin.com>]

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
implemented 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.

For that, a hook called ->attach_chip() is created in the
nand_controller structure. This structure may be referenced by two ways:
1/ if the driver does not implement its own controller, the
   chip->controller hook is not populated before nand_scan() so it
   cannot be dereferenced: use chip->hwcontrol instead (which is
   statically allocated and will be referenced later by chip->controller
   anyway).
2/ through chip->controller if the driver implements its own controller.

Another hook, ->detach_chip() is also introduced in order to clean the
controller driver's potential allocations in case of failure of
nand_scan_tail(). There is no need for the controller driver to call the
->detach_chip() hook directly upon error after a successful nand_scan().
In this situation, calling nand_release() as before is enough.

Both ->attac/detach_chip() hooks are located in a nand_controller_ops
structure.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 drivers/mtd/nand/raw/nand_base.c | 21 +++++++++++++++++++--
 include/linux/mtd/rawnand.h      | 16 ++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index e21f03ee3251..5e8278281ba8 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -6710,11 +6710,23 @@ 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;
+
+	if (chip->controller->ops && chip->controller->ops->attach_chip) {
+		ret = chip->controller->ops->attach_chip(chip);
+		if (ret)
+			return ret;
+	}
+
+	ret = nand_scan_tail(mtd);
+	if (ret && chip->controller->ops && chip->controller->ops->detach_chip)
+		chip->controller->ops->detach_chip(chip);
+
 	return ret;
 }
 EXPORT_SYMBOL(nand_scan_with_ids);
@@ -6742,7 +6754,12 @@ void nand_cleanup(struct nand_chip *chip)
 
 	/* Free manufacturer priv data. */
 	nand_manufacturer_cleanup(chip);
+
+	/* Free controller specific allocations after chip identification */
+	if (chip->controller->ops && chip->controller->ops->detach_chip)
+		chip->controller->ops->detach_chip(chip);
 }
+
 EXPORT_SYMBOL_GPL(nand_cleanup);
 
 /**
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index f5fb9caf6dca..d1f2267ae724 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -509,6 +509,19 @@ struct nand_id {
 	int len;
 };
 
+/**
+ * struct nand_controller_ops - Controller operations
+ *
+ * @attach_chip:	Callback that may be called between nand_detect() and
+ *			nand_scan_tail() during nand_scan() (optional).
+ * @detach_chip:	Callback that may be called if nand_scan_tail() fails
+ *			(optional).
+ */
+struct nand_controller_ops {
+	int (*attach_chip)(struct nand_chip *chip);
+	void (*detach_chip)(struct nand_chip *chip);
+};
+
 /**
  * struct nand_controller - Control structure for hardware controller
  *                          shared among independent devices
@@ -517,11 +530,13 @@ 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)
@@ -529,6 +544,7 @@ static inline void nand_controller_init(struct nand_controller *nfc)
 	nfc->active = NULL;
 	spin_lock_init(&nfc->lock);
 	init_waitqueue_head(&nfc->wq);
+	nfc->ops = NULL;
 }
 
 /**
-- 
2.14.1