spi: allow ancillary devices to share parent's chip selects

When registering an ancillary SPI device, the current code flags a chip
select conflict with the parent device. This happens because the
ancillary device intentionally uses one of the parent's chip selects,
but __spi_add_device() checks against all existing devices including
the parent.

Allow this by passing the parent device pointer to __spi_add_device()
and skipping the conflict check when the existing device is the parent.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/bcb1eb34fc5e86fd5dbb4472ad1d3ea3cf3e9779.1770393792.git.antoniu.miclaus@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 61f7bde8c7fbbccad315be98f4f6b863fc1e385b..8fbed4754de4e520ec21167254b9378f1c59e35b 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -641,12 +641,26 @@ static inline int spi_dev_check_cs(struct device *dev,
        return 0;
 }
 
+struct spi_dev_check_info {
+       struct spi_device *new_spi;
+       struct spi_device *parent;      /* set for ancillary devices */
+};
+
 static int spi_dev_check(struct device *dev, void *data)
 {
        struct spi_device *spi = to_spi_device(dev);
-       struct spi_device *new_spi = data;
+       struct spi_dev_check_info *info = data;
+       struct spi_device *new_spi = info->new_spi;
        int status, idx;
 
+       /*
+        * When registering an ancillary device, skip checking against the
+        * parent device since the ancillary is intentionally using one of
+        * the parent's chip selects.
+        */
+       if (info->parent && spi == info->parent)
+               return 0;
+
        if (spi->controller == new_spi->controller) {
                for (idx = 0; idx < spi->num_chipselect; idx++) {
                        status = spi_dev_check_cs(dev, spi, idx, new_spi, 0);
@@ -663,10 +677,11 @@ static void spi_cleanup(struct spi_device *spi)
                spi->controller->cleanup(spi);
 }
 
-static int __spi_add_device(struct spi_device *spi)
+static int __spi_add_device(struct spi_device *spi, struct spi_device *parent)
 {
        struct spi_controller *ctlr = spi->controller;
        struct device *dev = ctlr->dev.parent;
+       struct spi_dev_check_info check_info;
        int status, idx;
        u8 cs;
 
@@ -710,7 +725,9 @@ static int __spi_add_device(struct spi_device *spi)
         * chipselect **BEFORE** we call setup(), else we'll trash
         * its configuration.
         */
-       status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
+       check_info.new_spi = spi;
+       check_info.parent = parent;
+       status = bus_for_each_dev(&spi_bus_type, NULL, &check_info, spi_dev_check);
        if (status)
                return status;
 
@@ -772,7 +789,7 @@ int spi_add_device(struct spi_device *spi)
        spi_dev_set_name(spi);
 
        mutex_lock(&ctlr->add_lock);
-       status = __spi_add_device(spi);
+       status = __spi_add_device(spi, NULL);
        mutex_unlock(&ctlr->add_lock);
        return status;
 }
@@ -2715,8 +2732,8 @@ struct spi_device *spi_new_ancillary_device(struct spi_device *spi,
 
        WARN_ON(!mutex_is_locked(&ctlr->add_lock));
 
-       /* Register the new device */
-       rc = __spi_add_device(ancillary);
+       /* Register the new device, passing the parent to skip CS conflict check */
+       rc = __spi_add_device(ancillary, spi);
        if (rc) {
                dev_err(&spi->dev, "failed to register ancillary device\n");
                goto err_out;