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Commit 5090cc6a authored by Heiner Kallweit's avatar Heiner Kallweit Committed by Mark Brown
Browse files

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: default avatarHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 29b4817d

include/linux/spi/spi.h

+21 −4
Original line number Diff line number Diff line
@@ -312,6 +312,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) 
 * @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 @@ struct spi_master { 
#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 @@ 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)

spi_max_message_size(struct spi_device *spi)

{

	struct spi_master *master = spi->master;

	if (!master->max_transfer_size)

	if (!master->max_message_size)

		return SIZE_MAX;

	return master->max_transfer_size(spi);

	return master->max_message_size(spi);

}



static inline size_t

spi_max_transfer_size(struct spi_device *spi)

{

	struct spi_master *master = spi->master;

	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);

}



/*---------------------------------------------------------------------------*/