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Applied "spi: introduce max_message_size hook in spi_master" to the spi tree

Message ID E1baKOP-0002Ab-9s@debutante
State Not Applicable
Headers show

Commit Message

Mark Brown Aug. 18, 2016, 10:17 a.m. UTC
The patch

   spi: introduce max_message_size hook in spi_master

has been applied to the spi tree at


All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

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From 5090cc6ae2f79ee779e5faf7c8a28edf42b7d738 Mon Sep 17 00:00:00 2001
From: Heiner Kallweit <hkallweit1@gmail.com>
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 <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
 include/linux/spi/spi.h | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)
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diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 072cb2aa2413..f2d3960cc3c3 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -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;
@@ -905,12 +908,26 @@  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)
+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);