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spi: Make support for regular transfers optional when ->mem_ops != NULL 

Some SPI/QuadSPI controllers only expose a high-level SPI memory
interface, thus preventing any regular SPI transfers from being done.

In that case, SPI controller drivers can leave all ->transfer_xxx()
hooks empty and only implement the spi_mem_ops interface.

Adjust the core to allow such situations:
- extend spi_controller_check_ops() to accept situations where all
  ->transfer_xxx() pointers are NULL only if ->mem_ops != NULL
- make sure we do not initialize the SPI message queue if
  ctlr->transfer_one and ctlr->transfer_one_message are missing
- return -ENOTSUPP if someone tries to do a regular SPI transfer on
  a controller that does not support it

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@exceet.de>
Tested-by: Frieder Schrempf <frieder.schrempf@exceet.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Boris Brezillon 2018-04-26 18:18:15 +02:00 committed by Mark Brown
parent c36ff266dc
commit b5932f5c68
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GPG Key ID: 24D68B725D5487D0
1 changed files with 26 additions and 7 deletions
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33
drivers/spi/spi.c
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@ -28,6 +28,7 @@
#include <linux/slab.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi-mem.h>
#include <linux/of_gpio.h>
#include <linux/pm_runtime.h>
#include <linux/pm_domain.h>
@ -2071,12 +2072,19 @@ static int of_spi_register_master(struct spi_controller *ctlr)
static int spi_controller_check_ops(struct spi_controller *ctlr)
{
/*
* The controller must at least implement one of the ->transfer()
* hooks.
* The controller may implement only the high-level SPI-memory like
* operations if it does not support regular SPI transfers, and this is
* valid use case.
* If ->mem_ops is NULL, we request that at least one of the
* ->transfer_xxx() method be implemented.
*/
if (!ctlr->transfer && !ctlr->transfer_one &&
!ctlr->transfer_one_message)
if (ctlr->mem_ops) {
if (!ctlr->mem_ops->exec_op)
return -EINVAL;
} else if (!ctlr->transfer && !ctlr->transfer_one &&
!ctlr->transfer_one_message) {
return -EINVAL;
}
return 0;
}
@ -2187,10 +2195,14 @@ int spi_register_controller(struct spi_controller *ctlr)
spi_controller_is_slave(ctlr) ? "slave" : "master",
dev_name(&ctlr->dev));
/* If we're using a queued driver, start the queue */
if (ctlr->transfer)
/*
* If we're using a queued driver, start the queue. Note that we don't
* need the queueing logic if the driver is only supporting high-level
* memory operations.
*/
if (ctlr->transfer) {
dev_info(dev, "controller is unqueued, this is deprecated\n");
else {
} else if (ctlr->transfer_one || ctlr->transfer_one_message) {
status = spi_controller_initialize_queue(ctlr);
if (status) {
device_del(&ctlr->dev);
@ -2920,6 +2932,13 @@ static int __spi_async(struct spi_device *spi, struct spi_message *message)
{
struct spi_controller *ctlr = spi->controller;
/*
* Some controllers do not support doing regular SPI transfers. Return
* ENOTSUPP when this is the case.
*/
if (!ctlr->transfer)
return -ENOTSUPP;
message->spi = spi;
SPI_STATISTICS_INCREMENT_FIELD(&ctlr->statistics, spi_async);