[PATCHv3 1/5] spi: add ancillary device support

Sebastian Reichel
2021-05-28T11:36:57Z

Introduce support for ancillary devices, similar to existing
implementation for I2C. This is useful for devices having
multiple chip-selects, for example some microcontrollers
provide a normal SPI interface and a flashing SPI interface.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
drivers/spi/spi.c | 139 +++++++++++++++++++++++++++++++---------
include/linux/spi/spi.h | 2 +
2 files changed, 109 insertions(+), 32 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index ba425b9c7700..7fdf224262b1 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -558,49 +558,23 @@ static int spi_dev_check(struct device *dev, void *data)
return 0;
}

-/**
- * spi_add_device - Add spi_device allocated with spi_alloc_device
- * @spi: spi_device to register
- *
- * Companion function to spi_alloc_device. Devices allocated with
- * spi_alloc_device can be added onto the spi bus with this function.
- *
- * Return: 0 on success; negative errno on failure
- */
-int spi_add_device(struct spi_device *spi)
+static int __spi_add_device(struct spi_device *spi)
{
struct spi_controller *ctlr = spi->controller;
struct device *dev = ctlr->dev.parent;
int status;

- /* Chipselects are numbered 0..max; validate. */
- if (spi->chip_select >= ctlr->num_chipselect) {
- dev_err(dev, "cs%d >= max %d\n", spi->chip_select,
- ctlr->num_chipselect);
- return -EINVAL;
- }
-
- /* Set the bus ID string */
- spi_dev_set_name(spi);
-
- /* We need to make sure there's no other device with this
- * chipselect **BEFORE** we call setup(), else we'll trash
- * its configuration. Lock against concurrent add() calls.
- */
- mutex_lock(&spi_add_lock);
-
status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
if (status) {
dev_err(dev, "chipselect %d already in use\n",
spi->chip_select);
- goto done;
+ return status;
}

/* Controller may unregister concurrently */
if (IS_ENABLED(CONFIG_SPI_DYNAMIC) &&
!device_is_registered(&ctlr->dev)) {
- status = -ENODEV;
- goto done;
+ return -ENODEV;
}

/* Descriptors take precedence */
@@ -617,7 +591,7 @@ int spi_add_device(struct spi_device *spi)
if (status < 0) {
dev_err(dev, "can't setup %s, status %d\n",
dev_name(&spi->dev), status);
- goto done;
+ return status;
}

/* Device may be bound to an active driver when this returns */
@@ -628,12 +602,64 @@ int spi_add_device(struct spi_device *spi)
else
dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));

-done:
+ return status;
+}
+
+/**
+ * spi_add_device - Add spi_device allocated with spi_alloc_device
+ * @spi: spi_device to register
+ *
+ * Companion function to spi_alloc_device. Devices allocated with
+ * spi_alloc_device can be added onto the spi bus with this function.
+ *
+ * Return: 0 on success; negative errno on failure
+ */
+int spi_add_device(struct spi_device *spi)
+{
+ struct spi_controller *ctlr = spi->controller;
+ struct device *dev = ctlr->dev.parent;
+ int status;
+
+ /* Chipselects are numbered 0..max; validate. */
+ if (spi->chip_select >= ctlr->num_chipselect) {
+ dev_err(dev, "cs%d >= max %d\n", spi->chip_select,
+ ctlr->num_chipselect);
+ return -EINVAL;
+ }
+
+ /* Set the bus ID string */
+ spi_dev_set_name(spi);
+
+ /* We need to make sure there's no other device with this
+ * chipselect **BEFORE** we call setup(), else we'll trash
+ * its configuration. Lock against concurrent add() calls.
+ */
+ mutex_lock(&spi_add_lock);
+ status = __spi_add_device(spi);
mutex_unlock(&spi_add_lock);
return status;
}
EXPORT_SYMBOL_GPL(spi_add_device);

+static int spi_add_device_locked(struct spi_device *spi)
+{
+ struct spi_controller *ctlr = spi->controller;
+ struct device *dev = ctlr->dev.parent;
+
+ /* Chipselects are numbered 0..max; validate. */
+ if (spi->chip_select >= ctlr->num_chipselect) {
+ dev_err(dev, "cs%d >= max %d\n", spi->chip_select,
+ ctlr->num_chipselect);
+ return -EINVAL;
+ }
+
+ /* Set the bus ID string */
+ spi_dev_set_name(spi);
+
+ WARN_ON(!mutex_is_locked(&spi_add_lock));
+ return __spi_add_device(spi);
+}
+
/**
* spi_new_device - instantiate one new SPI device
* @ctlr: Controller to which device is connected
@@ -1993,7 +2019,7 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
}

/* Device address */
- rc = of_property_read_u32(nc, "reg", &value);
+ rc = of_property_read_u32_index(nc, "reg", 0, &value);
if (rc) {
dev_err(&ctlr->dev, "%pOF has no valid 'reg' property (%d)\n",
nc, rc);
@@ -2084,6 +2110,55 @@ static void of_register_spi_devices(struct spi_controller *ctlr)
static void of_register_spi_devices(struct spi_controller *ctlr) { }
#endif

+/**
+ * spi_new_ancillary_device() - Register ancillary SPI device
+ * @spi: Pointer to the main SPI device registering the ancillary device
+ * @chip_select: Chip Select of the ancillary device
+ *
+ * Register an ancillary SPI device; for example some chips have a chip-select
+ * for normal device usage and another one for setup/firmware upload.
+ *
+ * This may only be called from main SPI device's probe routine.
+ *
+ * Return: 0 on success; negative errno on failure
+ */
+struct spi_device *spi_new_ancillary_device(struct spi_device *spi,
+ u8 chip_select)
+{
+ struct spi_device *ancillary;
+ int rc = 0;
+
+ /* Alloc an spi_device */
+ ancillary = spi_alloc_device(spi->controller);
+ if (!ancillary) {
+ rc = -ENOMEM;
+ goto err_out;
+ }
+
+ strlcpy(ancillary->modalias, "dummy", sizeof(ancillary->modalias));
+
+ /* Use provided chip-select for ancillary device */
+ ancillary->chip_select = chip_select;
+
+ /* Take over SPI mode/speed from SPI main device */
+ ancillary->max_speed_hz = spi->max_speed_hz;
+ ancillary->mode = ancillary->mode;
+
+ /* Register the new device */
+ rc = spi_add_device_locked(ancillary);
+ if (rc) {
+ dev_err(&spi->dev, "failed to register ancillary device\n");
+ goto err_out;
+ }
+
+ return ancillary;
+
+err_out:
+ spi_dev_put(ancillary);
+ return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(spi_new_ancillary_device);
+
#ifdef CONFIG_ACPI
struct acpi_spi_lookup {
struct spi_controller *ctlr;
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 360a3bc767ca..1949230ccd3a 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -299,6 +299,8 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
driver_unregister(&sdrv->driver);
}

+extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 chip_select);
+
/* use a define to avoid include chaining to get THIS_MODULE */
#define spi_register_driver(driver) \
__spi_register_driver(THIS_MODULE, driver)
--
2.30.2