[PATCH] SPI core tweaks, bugfix
This includes various updates to the SPI core:
- Fixes a driver model refcount bug in spi_unregister_master() paths.
- The spi_master structures now have wrappers which help keep drivers
from needing class-level get/put for device data or for refcounts.
- Check for a few setup errors that would cause oopsing later.
- Docs say more about memory management. Highlights the use of DMA-safe
i/o buffers, and zero-initializing spi_message and such metadata.
- Provide a simple alloc/free for spi_message and its spi_transfer;
this is only one of the possible memory management policies.
Nothing to break code that already works.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c851b3d..6a41e26 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -60,8 +60,8 @@
u8 mode;
#define SPI_CPHA 0x01 /* clock phase */
#define SPI_CPOL 0x02 /* clock polarity */
-#define SPI_MODE_0 (0|0)
-#define SPI_MODE_1 (0|SPI_CPHA) /* (original MicroWire) */
+#define SPI_MODE_0 (0|0) /* (original MicroWire) */
+#define SPI_MODE_1 (0|SPI_CPHA)
#define SPI_MODE_2 (SPI_CPOL|0)
#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
#define SPI_CS_HIGH 0x04 /* chipselect active high? */
@@ -209,6 +209,30 @@
void (*cleanup)(const struct spi_device *spi);
};
+static inline void *spi_master_get_devdata(struct spi_master *master)
+{
+ return class_get_devdata(&master->cdev);
+}
+
+static inline void spi_master_set_devdata(struct spi_master *master, void *data)
+{
+ class_set_devdata(&master->cdev, data);
+}
+
+static inline struct spi_master *spi_master_get(struct spi_master *master)
+{
+ if (!master || !class_device_get(&master->cdev))
+ return NULL;
+ return master;
+}
+
+static inline void spi_master_put(struct spi_master *master)
+{
+ if (master)
+ class_device_put(&master->cdev);
+}
+
+
/* the spi driver core manages memory for the spi_master classdev */
extern struct spi_master *
spi_alloc_master(struct device *host, unsigned size);
@@ -271,11 +295,17 @@
* stay selected until the next transfer. This is purely a performance
* hint; the controller driver may need to select a different device
* for the next message.
+ *
+ * The code that submits an spi_message (and its spi_transfers)
+ * to the lower layers is responsible for managing its memory.
+ * Zero-initialize every field you don't set up explicitly, to
+ * insulate against future API updates.
*/
struct spi_transfer {
/* it's ok if tx_buf == rx_buf (right?)
* for MicroWire, one buffer must be null
- * buffers must work with dma_*map_single() calls
+ * buffers must work with dma_*map_single() calls, unless
+ * spi_message.is_dma_mapped reports a pre-existing mapping
*/
const void *tx_buf;
void *rx_buf;
@@ -302,6 +332,11 @@
* @status: zero for success, else negative errno
* @queue: for use by whichever driver currently owns the message
* @state: for use by whichever driver currently owns the message
+ *
+ * The code that submits an spi_message (and its spi_transfers)
+ * to the lower layers is responsible for managing its memory.
+ * Zero-initialize every field you don't set up explicitly, to
+ * insulate against future API updates.
*/
struct spi_message {
struct spi_transfer *transfers;
@@ -336,6 +371,29 @@
void *state;
};
+/* It's fine to embed message and transaction structures in other data
+ * structures so long as you don't free them while they're in use.
+ */
+
+static inline struct spi_message *spi_message_alloc(unsigned ntrans, gfp_t flags)
+{
+ struct spi_message *m;
+
+ m = kzalloc(sizeof(struct spi_message)
+ + ntrans * sizeof(struct spi_transfer),
+ flags);
+ if (m) {
+ m->transfers = (void *)(m + 1);
+ m->n_transfer = ntrans;
+ }
+ return m;
+}
+
+static inline void spi_message_free(struct spi_message *m)
+{
+ kfree(m);
+}
+
/**
* spi_setup -- setup SPI mode and clock rate
* @spi: the device whose settings are being modified
@@ -363,7 +421,10 @@
* The completion callback is invoked in a context which can't sleep.
* Before that invocation, the value of message->status is undefined.
* When the callback is issued, message->status holds either zero (to
- * indicate complete success) or a negative error code.
+ * indicate complete success) or a negative error code. After that
+ * callback returns, the driver which issued the transfer request may
+ * deallocate the associated memory; it's no longer in use by any SPI
+ * core or controller driver code.
*
* Note that although all messages to a spi_device are handled in
* FIFO order, messages may go to different devices in other orders.
@@ -445,6 +506,7 @@
return spi_sync(spi, &m);
}
+/* this copies txbuf and rxbuf data; for small transfers only! */
extern int spi_write_then_read(struct spi_device *spi,
const u8 *txbuf, unsigned n_tx,
u8 *rxbuf, unsigned n_rx);
@@ -555,8 +617,9 @@
/* If you're hotplugging an adapter with devices (parport, usb, etc)
- * use spi_new_device() to describe each device. You would then call
- * spi_unregister_device() to start making that device vanish.
+ * use spi_new_device() to describe each device. You can also call
+ * spi_unregister_device() to start making that device vanish, but
+ * normally that would be handled by spi_unregister_master().
*/
extern struct spi_device *
spi_new_device(struct spi_master *, struct spi_board_info *);