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Commit 4acad4aa authored by Michal Suchanek's avatar Michal Suchanek Committed by Mark Brown
Browse files

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: default avatarMichal Suchanek <hramrach@gmail.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 8005c49d

include/linux/spi/spi.h

+15 −0
Original line number Original line Diff line number Diff line
@@ -425,6 +425,12 @@ struct spi_master { 
#define SPI_MASTER_MUST_RX      BIT(3)		/* requires rx */

#define SPI_MASTER_MUST_RX      BIT(3)		/* requires rx */

#define SPI_MASTER_MUST_TX      BIT(4)		/* requires tx */

#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 */

	/* lock and mutex for SPI bus locking */

	spinlock_t		bus_lock_spinlock;

	spinlock_t		bus_lock_spinlock;

	struct mutex		bus_lock_mutex;

	struct mutex		bus_lock_mutex;
@@ -832,6 +838,15 @@ extern int spi_async(struct spi_device *spi, struct spi_message *message); 
extern int spi_async_locked(struct spi_device *spi,

extern int spi_async_locked(struct spi_device *spi,

			    struct spi_message *message);

			    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

/* All these synchronous SPI transfer routines are utilities layered