usb: ljca: Improve ACPI hardware ID documentation

Document the differences between the LJCA client device ACPI hardware IDs,
including the USBIO IDs used for LJCA devices.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Hans de Goede <hansg@kernel.org>
Link: https://lore.kernel.org/r/20251010055625.4147844-2-sakari.ailus@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/misc/usb-ljca.c b/drivers/usb/misc/usb-ljca.c
index dc2ad31ae1524c39b218589f62e23fa251a1e317..9e65bb9577ea17b544d943e799b37a8c878edf82 100644 (file)
--- a/drivers/usb/misc/usb-ljca.c
+++ b/drivers/usb/misc/usb-ljca.c
@@ -164,28 +164,39 @@ struct ljca_match_ids_walk_data {
        struct acpi_device *adev;
 };
 
+/*
+ * ACPI hardware IDs for LJCA client devices.
+ *
+ * [1] Some BIOS implementations use these IDs for denoting LJCA client devices
+ *     even though the IDs have been allocated for USBIO. This isn't a problem
+ *     as the usb-ljca driver is probed based on the USB device's vendor and
+ *     product IDs and its client drivers are probed based on auxiliary device
+ *     names, not these ACPI _HIDs. List of such systems:
+ *
+ *     Dell Precision 5490
+ */
 static const struct acpi_device_id ljca_gpio_hids[] = {
-       { "INTC100B" },
-       { "INTC1074" },
-       { "INTC1096" },
-       { "INTC10B5" },
-       { "INTC10D1" },
+       { "INTC100B" }, /* RPL LJCA GPIO */
+       { "INTC1074" }, /* CVF LJCA GPIO */
+       { "INTC1096" }, /* ADL LJCA GPIO */
+       { "INTC10B5" }, /* LNL LJCA GPIO */
+       { "INTC10D1" }, /* MTL (CVF VSC) USBIO GPIO [1] */
        {},
 };
 
 static const struct acpi_device_id ljca_i2c_hids[] = {
-       { "INTC100C" },
-       { "INTC1075" },
-       { "INTC1097" },
-       { "INTC10D2" },
+       { "INTC100C" }, /* RPL LJCA I2C */
+       { "INTC1075" }, /* CVF LJCA I2C */
+       { "INTC1097" }, /* ADL LJCA I2C */
+       { "INTC10D2" }, /* MTL (CVF VSC) USBIO I2C [1] */
        {},
 };
 
 static const struct acpi_device_id ljca_spi_hids[] = {
-       { "INTC100D" },
-       { "INTC1091" },
-       { "INTC1098" },
-       { "INTC10D3" },
+       { "INTC100D" }, /* RPL LJCA SPI */
+       { "INTC1091" }, /* TGL/ADL LJCA SPI */
+       { "INTC1098" }, /* ADL LJCA SPI */
+       { "INTC10D3" }, /* MTL (CVF VSC) USBIO SPI [1] */
        {},
 };