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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>
This commit is contained in:
Heiner Kallweit 2016-08-17 21:08:01 +02:00 committed by Mark Brown
parent 29b4817d40
commit 5090cc6ae2
1 changed files with 21 additions and 4 deletions
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25
include/linux/spi/spi.h
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@ -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;
@ -904,13 +907,27 @@ extern int spi_async(struct spi_device *spi, struct spi_message *message);
extern int spi_async_locked(struct spi_device *spi,
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);
}
/*---------------------------------------------------------------------------*/