spi: enable spi_board_info to be registered after spi_master

Currently spi_register_board_info() has to be called before its related
spi_master be registered, otherwise these board info will be just ignored.

This patch will remove this order limit, it adds a global spi master list
like the existing global board info listr. Whenever a board info or a
spi_master is registered, the spi master list or board info list
will be scanned, and a new spi device will be created if there is a
master-board info match.
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi.c

@@ -29,11 +29,6 @@
 #include <linux/spi/spi.h>
 #include <linux/of_spi.h>
 
-
-/* SPI bustype and spi_master class are registered after board init code
- * provides the SPI device tables, ensuring that both are present by the
- * time controller driver registration causes spi_devices to "enumerate".
- */
 static void spidev_release(struct device *dev)
 {
 	struct spi_device	*spi = to_spi_device(dev);
@@ -202,11 +197,16 @@ EXPORT_SYMBOL_GPL(spi_register_driver);
 
 struct boardinfo {
 	struct list_head	list;
-	unsigned		n_board_info;
-	struct spi_board_info	board_info[0];
+	struct spi_board_info	board_info;
 };
 
 static LIST_HEAD(board_list);
+static LIST_HEAD(spi_master_list);
+
+/*
+ * Used to protect add/del opertion for board_info list and
+ * spi_master list, and their matching process
+ */
 static DEFINE_MUTEX(board_lock);
 
 /**
@@ -371,6 +371,20 @@ struct spi_device *spi_new_device(struct spi_master *master,
 }
 EXPORT_SYMBOL_GPL(spi_new_device);
 
+static void spi_match_master_to_boardinfo(struct spi_master *master,
+				struct spi_board_info *bi)
+{
+	struct spi_device *dev;
+
+	if (master->bus_num != bi->bus_num)
+		return;
+
+	dev = spi_new_device(master, bi);
+	if (!dev)
+		dev_err(master->dev.parent, "can't create new device for %s\n",
+			bi->modalias);
+}
+
 /**
  * spi_register_board_info - register SPI devices for a given board
  * @info: array of chip descriptors
@@ -394,42 +408,24 @@ int __init
 spi_register_board_info(struct spi_board_info const *info, unsigned n)
 {
 	struct boardinfo *bi;
+	int i;
 
-	bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
+	bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
 	if (!bi)
 		return -ENOMEM;
-	bi->n_board_info = n;
-	memcpy(bi->board_info, info, n * sizeof *info);
 
+	for (i = 0; i < n; i++, bi++, info++) {
+		struct spi_master *master;
+
+		memcpy(&bi->board_info, info, sizeof(*info));
 		mutex_lock(&board_lock);
 		list_add_tail(&bi->list, &board_list);
+		list_for_each_entry(master, &spi_master_list, list)
+			spi_match_master_to_boardinfo(master, &bi->board_info);
 		mutex_unlock(&board_lock);
-	return 0;
-}
-
-/* FIXME someone should add support for a __setup("spi", ...) that
- * creates board info from kernel command lines
- */
-
-static void scan_boardinfo(struct spi_master *master)
-{
-	struct boardinfo	*bi;
-
-	mutex_lock(&board_lock);
-	list_for_each_entry(bi, &board_list, list) {
-		struct spi_board_info	*chip = bi->board_info;
-		unsigned		n;
-
-		for (n = bi->n_board_info; n > 0; n--, chip++) {
-			if (chip->bus_num != master->bus_num)
-				continue;
-			/* NOTE: this relies on spi_new_device to
-			 * issue diagnostics when given bogus inputs
-			 */
-			(void) spi_new_device(master, chip);
-		}
 	}
-	mutex_unlock(&board_lock);
+
+	return 0;
 }
 
 /*-------------------------------------------------------------------------*/
@@ -512,6 +508,7 @@ int spi_register_master(struct spi_master *master)
 {
 	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
 	struct device		*dev = master->dev.parent;
+	struct boardinfo	*bi;
 	int			status = -ENODEV;
 	int			dynamic = 0;
 
@@ -547,8 +544,12 @@ int spi_register_master(struct spi_master *master)
 	dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
 			dynamic ? " (dynamic)" : "");
 
-	/* populate children from any spi device tables */
-	scan_boardinfo(master);
+	mutex_lock(&board_lock);
+	list_add_tail(&master->list, &spi_master_list);
+	list_for_each_entry(bi, &board_list, list)
+		spi_match_master_to_boardinfo(master, &bi->board_info);
+	mutex_unlock(&board_lock);
+
 	status = 0;
 
 	/* Register devices from the device tree */
@@ -579,7 +580,12 @@ void spi_unregister_master(struct spi_master *master)
 {
 	int dummy;
 
-	dummy = device_for_each_child(&master->dev, NULL, __unregister);
+	mutex_lock(&board_lock);
+	list_del(&master->list);
+	mutex_unlock(&board_lock);
+
+	dummy = device_for_each_child(master->dev.parent, &master->dev,
+					__unregister);
 	device_unregister(&master->dev);
 }
 EXPORT_SYMBOL_GPL(spi_unregister_master);

include/linux/spi/spi.h

@@ -204,6 +204,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
 /**
  * struct spi_master - interface to SPI master controller
  * @dev: device interface to this driver
+ * @list: link with the global spi_master list
  * @bus_num: board-specific (and often SOC-specific) identifier for a
  *	given SPI controller.
  * @num_chipselect: chipselects are used to distinguish individual
@@ -238,6 +239,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
 struct spi_master {
 	struct device	dev;
 
+	struct list_head list;
+
 	/* other than negative (== assign one dynamically), bus_num is fully
 	 * board-specific.  usually that simplifies to being SOC-specific.
 	 * example:  one SOC has three SPI controllers, numbered 0..2,