spi: introduce max_message_size hook in spi_master
Recently a maximum transfer size was was introduced in struct spi_master.
However there are also spi controllers with a maximum message size, e.g.
fsl-espi has a max message size of 64KB.
Introduce a hook max_message_size to deal with such limitations.
Also make sure that spi_max_transfer_size doesn't return greater values
than spi_max_message_size, even if hook max_transfer_size is not set.
Signed-off-by: Heiner Kallweit <hkallweit1@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 072cb2a..f2d3960 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -312,6 +312,8 @@
* @flags: other constraints relevant to this driver
* @max_transfer_size: function that returns the max transfer size for
* a &spi_device; may be %NULL, so the default %SIZE_MAX will be used.
+ * @max_message_size: function that returns the max message size for
+ * a &spi_device; may be %NULL, so the default %SIZE_MAX will be used.
* @io_mutex: mutex for physical bus access
* @bus_lock_spinlock: spinlock for SPI bus locking
* @bus_lock_mutex: mutex for exclusion of multiple callers
@@ -442,10 +444,11 @@
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
/*
- * on some hardware transfer size may be constrained
+ * on some hardware transfer / message size may be constrained
* the limit may depend on device transfer settings
*/
size_t (*max_transfer_size)(struct spi_device *spi);
+ size_t (*max_message_size)(struct spi_device *spi);
/* I/O mutex */
struct mutex io_mutex;
@@ -905,12 +908,26 @@
struct spi_message *message);
static inline size_t
+spi_max_message_size(struct spi_device *spi)
+{
+ struct spi_master *master = spi->master;
+ if (!master->max_message_size)
+ return SIZE_MAX;
+ return master->max_message_size(spi);
+}
+
+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);
+ size_t tr_max = SIZE_MAX;
+ size_t msg_max = spi_max_message_size(spi);
+
+ if (master->max_transfer_size)
+ tr_max = master->max_transfer_size(spi);
+
+ /* transfer size limit must not be greater than messsage size limit */
+ return min(tr_max, msg_max);
}
/*---------------------------------------------------------------------------*/