diff options
Diffstat (limited to 'target/linux/brcm63xx/patches-4.4/000-4.5-20-spi-expose-master-transfer-size-limitation.patch')
| -rw-r--r-- | target/linux/brcm63xx/patches-4.4/000-4.5-20-spi-expose-master-transfer-size-limitation.patch | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/target/linux/brcm63xx/patches-4.4/000-4.5-20-spi-expose-master-transfer-size-limitation.patch b/target/linux/brcm63xx/patches-4.4/000-4.5-20-spi-expose-master-transfer-size-limitation.patch new file mode 100644 index 0000000..21e037c --- /dev/null +++ b/target/linux/brcm63xx/patches-4.4/000-4.5-20-spi-expose-master-transfer-size-limitation.patch @@ -0,0 +1,51 @@ +From 4acad4aae10d1fa79a075b38b5c73772c44f576c Mon Sep 17 00:00:00 2001 +From: Michal Suchanek <hramrach@gmail.com> +Date: Wed, 2 Dec 2015 10:38:21 +0000 +Subject: [PATCH] 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: Michal Suchanek <hramrach@gmail.com> +Signed-off-by: Mark Brown <broonie@kernel.org> +--- + include/linux/spi/spi.h | 15 +++++++++++++++ + 1 file changed, 15 insertions(+) + +--- a/include/linux/spi/spi.h ++++ b/include/linux/spi/spi.h +@@ -428,6 +428,12 @@ struct spi_master { + #define SPI_MASTER_MUST_RX BIT(3) /* requires rx */ + #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 */ + spinlock_t bus_lock_spinlock; + struct mutex bus_lock_mutex; +@@ -837,6 +843,15 @@ extern int spi_async(struct spi_device * + 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) ++{ ++ 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 |