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include/spi: Clarify spi_release() function behavior

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It will unlock and unhold the CS line. Note that the lock and the CS
being hold on are 2 separate config bits, so if only one is selected
spi_release() will only apply on this configuration.

Note: this has been already the case in the controller drivers, where
there implementation of spi_release() calls
spi_context_unlock_unconditionally(). And that function always forces
the CS line to an inactive state.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
This commit is contained in:
Tomasz Bursztyka 2021-11-08 14:23:17 +01:00 • committed by Anas Nashif
commit 60827c2dd6
1 changed files with 10 additions and 12 deletions
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22
include/drivers/spi.h
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@ -235,10 +235,6 @@ struct spi_cs_control {
* @param slave is the slave number from 0 to host controller slave limit.
* @param cs is a valid pointer on a struct spi_cs_control is CS line is
* emulated through a gpio line, or NULL otherwise.
*
* @note Only cs_hold and lock_on can be changed between consecutive
* transceive call. Rest of the attributes are not meant to be tweaked.
*
* @warning Most drivers use pointer comparison to determine whether a
* passed configuration is different from one used in a previous
* transaction. Changes to fields in the structure may not be
@ -684,19 +680,21 @@ static inline int spi_write_async(const struct device *dev,
#endif /* CONFIG_SPI_ASYNC */
/**
* @brief Release the SPI device locked on by the current config
* @brief Release the SPI device locked on and/or the CS by the current config
*
* Note: This synchronous function is used to release the lock on the SPI
* device that was kept if, and if only, given config parameter was
* the last one to be used (in any of the above functions) and if
* it has the SPI_LOCK_ON bit set into its operation bits field.
* Note: This synchronous function is used to release either the lock on the
* SPI device and/or the CS line that was kept if, and if only,
* given config parameter was the last one to be used (in any of the
* above functions) and if it has the SPI_LOCK_ON bit set and/or the
* SPI_HOLD_ON_CS bit set into its operation bits field.
* This can be used if the caller needs to keep its hand on the SPI
* device for consecutive transactions.
* device for consecutive transactions and/or if it needs the device to
* stay selected. Usually both bits will be used along each other, so the
* the device is locked and stays on until another operation is necessary
* or until it gets released with the present function.
*
* @param dev Pointer to the device structure for the driver instance
* @param config Pointer to a valid spi_config structure instance.
* Pointer-comparison may be used to detect changes from
* previous operations.
*
* @retval 0 If successful.
* @retval -errno Negative errno code on failure.