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52 lines
1.7 KiB
Diff
52 lines
1.7 KiB
Diff
From 4acad4aae10d1fa79a075b38b5c73772c44f576c Mon Sep 17 00:00:00 2001
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From: Michal Suchanek <hramrach@gmail.com>
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Date: Wed, 2 Dec 2015 10:38:21 +0000
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Subject: [PATCH] spi: expose master transfer size limitation.
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On some SPI controllers it is not feasible to transfer arbitrary amount
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of data at once.
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When the limit on transfer size is a few kilobytes at least it makes
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sense to use the SPI hardware rather than reverting to gpio driver.
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The protocol drivers need a way to check that they do not sent overly
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long messages, though.
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Signed-off-by: Michal Suchanek <hramrach@gmail.com>
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Signed-off-by: Mark Brown <broonie@kernel.org>
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---
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include/linux/spi/spi.h | 15 +++++++++++++++
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1 file changed, 15 insertions(+)
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--- a/include/linux/spi/spi.h
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+++ b/include/linux/spi/spi.h
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@@ -428,6 +428,12 @@ struct spi_master {
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#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
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#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
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+ /*
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+ * on some hardware transfer size may be constrained
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+ * the limit may depend on device transfer settings
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+ */
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+ size_t (*max_transfer_size)(struct spi_device *spi);
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+
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/* lock and mutex for SPI bus locking */
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spinlock_t bus_lock_spinlock;
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struct mutex bus_lock_mutex;
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@@ -837,6 +843,15 @@ extern int spi_async(struct spi_device *
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extern int spi_async_locked(struct spi_device *spi,
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struct spi_message *message);
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+static inline size_t
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+spi_max_transfer_size(struct spi_device *spi)
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+{
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+ struct spi_master *master = spi->master;
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+ if (!master->max_transfer_size)
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+ return SIZE_MAX;
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+ return master->max_transfer_size(spi);
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+}
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+
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/*---------------------------------------------------------------------------*/
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/* All these synchronous SPI transfer routines are utilities layered
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