From 5090cc6ae2f79ee779e5faf7c8a28edf42b7d738 Mon Sep 17 00:00:00 2001 From: Heiner Kallweit Date: Wed, 17 Aug 2016 21:08:01 +0200 Subject: [PATCH] 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 Signed-off-by: Mark Brown --- include/linux/spi/spi.h | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -304,6 +304,8 @@ static inline void spi_unregister_driver * @min_speed_hz: Lowest supported transfer speed * @max_speed_hz: Highest supported transfer speed * @flags: other constraints relevant to this driver + * @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. * @bus_lock_spinlock: spinlock for SPI bus locking * @bus_lock_mutex: mutex for SPI bus locking * @bus_lock_flag: indicates that the SPI bus is locked for exclusive use @@ -429,10 +431,11 @@ 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); /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; @@ -844,12 +847,26 @@ extern int spi_async_locked(struct spi_d 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); } /*---------------------------------------------------------------------------*/