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spi: Add SPI_NO_TX/RX support

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Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
might be missing from an ADC while for a DAC the MISO/RX line may be
optional. This patch adds these two new modes: SPI_NO_TX and
SPI_NO_RX. This way, the drivers will be able to identify if any of
these two lines is missing and to adjust the transfers accordingly.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201221152936.53873-2-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Dragos Bogdan
2020-12-21 17:29:35 +02:00
committed by Mark Brown
parent f7005142da
commit d962608ce2
3 changed files with 47 additions and 5 deletions
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17
include/linux/spi/spi.h
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@@ -6,6 +6,7 @@
#ifndef __LINUX_SPI_H
#define __LINUX_SPI_H
#include <linux/bits.h>
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/slab.h>
@@ -166,6 +167,18 @@ struct spi_device {
u8 chip_select;
u8 bits_per_word;
bool rt;
#define SPI_NO_TX BIT(31) /* no transmit wire */
#define SPI_NO_RX BIT(30) /* no receive wire */
/*
* All bits defined above should be covered by SPI_MODE_KERNEL_MASK.
* The SPI_MODE_KERNEL_MASK has the SPI_MODE_USER_MASK counterpart,
* which is defined in 'include/uapi/linux/spi/spi.h'.
* The bits defined here are from bit 31 downwards, while in
* SPI_MODE_USER_MASK are from 0 upwards.
* These bits must not overlap. A static assert check should make sure of that.
* If adding extra bits, make sure to decrease the bit index below as well.
*/
#define SPI_MODE_KERNEL_MASK (~(BIT(30) - 1))
u32 mode;
int irq;
void *controller_state;
@@ -189,6 +202,10 @@ struct spi_device {
*/
};
/* Make sure that SPI_MODE_KERNEL_MASK & SPI_MODE_USER_MASK don't overlap */
static_assert((SPI_MODE_KERNEL_MASK & SPI_MODE_USER_MASK) == 0,
"SPI_MODE_USER_MASK & SPI_MODE_KERNEL_MASK must not overlap");
static inline struct spi_device *to_spi_device(struct device *dev)
{
return dev ? container_of(dev, struct spi_device, dev) : NULL;