spi: expose master transfer size limitation.
On some SPI controllers it is not feasible to transfer arbitrary amount
of data at once.
When the limit on transfer size is a few kilobytes at least it makes
sense to use the SPI hardware rather than reverting to gpio driver.
The protocol drivers need a way to check that they do not sent overly
long messages, though.
Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index cce80e6..3eebc6c 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -425,6 +425,12 @@
#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
+ /*
+ * on some hardware transfer size may be constrained
+ * the limit may depend on device transfer settings
+ */
+ size_t (*max_transfer_size)(struct spi_device *spi);
+
/* lock and mutex for SPI bus locking */
spinlock_t bus_lock_spinlock;
struct mutex bus_lock_mutex;
@@ -832,6 +838,15 @@
extern int spi_async_locked(struct spi_device *spi,
struct spi_message *message);
+static inline size_t
+spi_max_transfer_size(struct spi_device *spi)
+{
+ struct spi_master *master = spi->master;
+ if (!master->max_transfer_size)
+ return SIZE_MAX;
+ return master->max_transfer_size(spi);
+}
+
/*---------------------------------------------------------------------------*/
/* All these synchronous SPI transfer routines are utilities layered