[PATCH v4 5/9] spi: expand device name to include enabled CS lines for multi-CS devices

[Jonathan Santos]

The device name for SPI devices was formatted as <controller>.<cs0>,
always using only the first chip-select index, ignoring the remaining CS
lines.

Change the naming format to <controller>.<cs0>-<csN> for multi-cs
devices so that the range of active chip-selects is reflected in the
device name. Since we are not expecting sparse values for logical CS
values, adopt the range format.

Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
---
Changes in v4:
* Opted for the range format, since we decide to limit logical CS values
  to a contiguous sequence.

Changes in v3:
* replaced `int idx = 1` by `unsigned int idx = 1` in the for loop.

Changes in v2:
* New patch.
---
 drivers/spi/spi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 2b2eeaa4c15d..53d6ab4ce8a3 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -782,6 +782,7 @@ static void spi_dev_set_name(struct spi_device *spi)
 {
 	struct device *dev = &spi->dev;
 	struct fwnode_handle *fwnode = dev_fwnode(dev);
+	u8 num_enabled_cs = hweight32(spi->cs_index_mask);
 
 	if (is_acpi_device_node(fwnode)) {
 		dev_set_name(dev, "spi-%s", acpi_dev_name(to_acpi_device_node(fwnode)));
@@ -793,6 +794,19 @@ static void spi_dev_set_name(struct spi_device *spi)
 		return;
 	}
 
+	/*
+	 * In multi-CS arrangements, use num_enabled_cs (derived from
+	 * cs_index_mask) to determine which CS lines the device is actively
+	 * using. num_chipselect only reflects how many CS lines are assigned
+	 * to the device, not how many are actually enabled.
+	 */
+	if (num_enabled_cs > 1) {
+		dev_set_name(&spi->dev, "%s.%u-%u", dev_name(&spi->controller->dev),
+			     spi_get_chipselect(spi, 0),
+			     spi_get_chipselect(spi, num_enabled_cs - 1));
+		return;
+	}
+
 	dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->controller->dev),
 		     spi_get_chipselect(spi, 0));
 }
-- 
2.34.1