The patch titled
spi doc updates
has been added to the -mm tree. Its filename is
spi-doc-updates.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
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------------------------------------------------------
Subject: spi doc updates
From: David Brownell <david-b@xxxxxxxxxxx>
Update two points in the SPI interface documentation:
- Update description of the "chip stays selected after message ends"
mode. In some cases it's required for correctness; it isn't just a
performance tweak. (Yes: to use this mode on mult-device busses, another
programming interface will be needed. One draft has been circulated
already.)
- Clarify spi_setup(), highlighting that callers must ensure that no
requests are queued (can't change configuration except between I/Os), and
that the device must be deselected when this returns (which is a key part
of why it's called during device init).
Signed-off-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/spi/spi.h | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff -puN include/linux/spi/spi.h~spi-doc-updates include/linux/spi/spi.h
--- a/include/linux/spi/spi.h~spi-doc-updates
+++ a/include/linux/spi/spi.h
@@ -341,9 +341,14 @@ extern struct spi_master *spi_busnum_to_
* chip transactions together.
*
* (ii) When the transfer is the last one in the message, the chip may
- * stay selected until the next transfer. This is purely a performance
- * hint; the controller driver may need to select a different device
- * for the next message.
+ * stay selected until the next transfer. On multi-device SPI busses
+ * with nothing blocking messages going to other devices, this is just
+ * a performance hint; starting a message to another device deselects
+ * this one. But in other cases, this can be used to ensure correctness.
+ * Some devices need protocol transactions to be built from a series of
+ * spi_message submissions, where the content of one message is determined
+ * by the results of previous messages and where the whole transaction
+ * ends when the chipselect goes intactive.
*
* The code that submits an spi_message (and its spi_transfers)
* to the lower layers is responsible for managing its memory.
@@ -480,14 +485,15 @@ static inline void spi_message_free(stru
/**
* spi_setup - setup SPI mode and clock rate
* @spi: the device whose settings are being modified
- * Context: can sleep
+ * Context: can sleep, and no requests are queued to the device
*
* SPI protocol drivers may need to update the transfer mode if the
- * device doesn't work with the mode 0 default. They may likewise need
+ * device doesn't work with its default. They may likewise need
* to update clock rates or word sizes from initial values. This function
* changes those settings, and must be called from a context that can sleep.
- * The changes take effect the next time the device is selected and data
- * is transferred to or from it.
+ * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
+ * effect the next time the device is selected and data is transferred to
+ * or from it. When this function returns, the spi device is deselected.
*
* Note that this call will fail if the protocol driver specifies an option
* that the underlying controller or its driver does not support. For
_
Patches currently in -mm which might be from david-b@xxxxxxxxxxx are
spi-doc-updates.patch
git-avr32.patch
git-leds.patch
git-mmc.patch
git-backlight.patch
char-genrtc-use-wait_event_interruptible.patch
spi-controller-drivers-check-for-unsupported-modes.patch
spi-controller-drivers-check-for-unsupported-modes-update.patch
spi-add-3wire-mode-flag.patch
spi-add-3wire-mode-flag-fix.patch
spidev-compiler-warning-gone.patch
spi_lm70llp-parport-adapter-driver-correction.patch
spi_mpc83xxc-underclocking-hotfix.patch
atmel_spi-minor-updates.patch
s3c24xx-spi-controllers-both-select-bitbang.patch
rtc-ds1307-cleanups.patch
rtc-rs5c372-becomes-a-new-style-i2c-driver.patch
thecus-n2100-register-rtc-rs5c372-i2c-device.patch
rtc-make-example-code-jump-to-done-instead-of-return-when-ioctl-not-supported.patch
rtc-dev-return-enotty-in-ioctl-if-irq_set_freq-is-not-implemented-by-driver.patch
driver-for-the-atmel-on-chip-rtc-on-at32ap700x-devices.patch
driver-for-the-atmel-on-chip-rtc-on-at32ap700x-devices-fix.patch
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