spi device setup gets better error checking

This updates some error reporting paths in SPI device setup:

 - Move validation logic for SPI chipselects to spi_new_device(),
   which is where it should always have been.

 - In spi_new_device(), emit error messages if the device can't
   be created.  This is LOTS better than a silent failure; though
   eventually, the calling convention should probably change to
   use the <linux/err.h> conventions.

 - Includes one previously-missing check:  SPI masters must always
   have at least one chipselect, even for dedicated busses which
   always keep it selected!

It also adds a FIXME (IDR for dynamic ID allocation) so the issue doesn't live
purely in my mailbox.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b05de30..e84d215 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -200,6 +200,8 @@ static DEFINE_MUTEX(board_lock);
  * platforms may not be able to use spi_register_board_info though, and
  * this is exported so that for example a USB or parport based adapter
  * driver could add devices (which it would learn about out-of-band).
+ *
+ * Returns the new device, or NULL.
  */
 struct spi_device *spi_new_device(struct spi_master *master,
                                  struct spi_board_info *chip)
@@ -208,7 +210,20 @@ struct spi_device *spi_new_device(struct spi_master *master,
        struct device           *dev = master->cdev.dev;
        int                     status;
 
-       /* NOTE:  caller did any chip->bus_num checks necessary */
+       /* NOTE:  caller did any chip->bus_num checks necessary.
+        *
+        * Also, unless we change the return value convention to use
+        * error-or-pointer (not NULL-or-pointer), troubleshootability
+        * suggests syslogged diagnostics are best here (ugh).
+        */
+
+       /* Chipselects are numbered 0..max; validate. */
+       if (chip->chip_select >= master->num_chipselect) {
+               dev_err(dev, "cs%d > max %d\n",
+                       chip->chip_select,
+                       master->num_chipselect);
+               return NULL;
+       }
 
        if (!spi_master_get(master))
                return NULL;
@@ -236,10 +251,10 @@ struct spi_device *spi_new_device(struct spi_master *master,
        proxy->controller_state = NULL;
        proxy->dev.release = spidev_release;
 
-       /* drivers may modify this default i/o setup */
+       /* drivers may modify this initial i/o setup */
        status = master->setup(proxy);
        if (status < 0) {
-               dev_dbg(dev, "can't %s %s, status %d\n",
+               dev_err(dev, "can't %s %s, status %d\n",
                                "setup", proxy->dev.bus_id, status);
                goto fail;
        }
@@ -249,7 +264,7 @@ struct spi_device *spi_new_device(struct spi_master *master,
         */
        status = device_register(&proxy->dev);
        if (status < 0) {
-               dev_dbg(dev, "can't %s %s, status %d\n",
+               dev_err(dev, "can't %s %s, status %d\n",
                                "add", proxy->dev.bus_id, status);
                goto fail;
        }
@@ -306,7 +321,6 @@ spi_register_board_info(struct spi_board_info const *info, unsigned n)
 static void scan_boardinfo(struct spi_master *master)
 {
        struct boardinfo        *bi;
-       struct device           *dev = master->cdev.dev;
 
        mutex_lock(&board_lock);
        list_for_each_entry(bi, &board_list, list) {
@@ -316,17 +330,9 @@ static void scan_boardinfo(struct spi_master *master)
                for (n = bi->n_board_info; n > 0; n--, chip++) {
                        if (chip->bus_num != master->bus_num)
                                continue;
-                       /* some controllers only have one chip, so they
-                        * might not use chipselects.  otherwise, the
-                        * chipselects are numbered 0..max.
+                       /* NOTE: this relies on spi_new_device to
+                        * issue diagnostics when given bogus inputs
                         */
-                       if (chip->chip_select >= master->num_chipselect
-                                       && master->num_chipselect) {
-                               dev_dbg(dev, "cs%d > max %d\n",
-                                       chip->chip_select,
-                                       master->num_chipselect);
-                               continue;
-                       }
                        (void) spi_new_device(master, chip);
                }
        }
@@ -419,8 +425,17 @@ int spi_register_master(struct spi_master *master)
        if (!dev)
                return -ENODEV;
 
+       /* even if it's just one always-selected device, there must
+        * be at least one chipselect
+        */
+       if (master->num_chipselect == 0)
+               return -EINVAL;
+
        /* convention:  dynamically assigned bus IDs count down from the max */
        if (master->bus_num < 0) {
+               /* FIXME switch to an IDR based scheme, something like
+                * I2C now uses, so we can't run out of "dynamic" IDs
+                */
                master->bus_num = atomic_dec_return(&dyn_bus_id);
                dynamic = 1;
        }