From 2c6c6001d07758cf79fc57c705b763d955e1922c Mon Sep 17 00:00:00 2001 From: Hui Wang Date: Fri, 11 Dec 2020 10:18:14 +0800 Subject: [PATCH] ACPI: PNP: compare the string length in the matching_id() commit b08221c40febcbda9309dd70c61cf1b0ebb0e351 upstream. Recently we met a touchscreen problem on some Thinkpad machines, the touchscreen driver (i2c-hid) is not loaded and the touchscreen can't work. An i2c ACPI device with the name WACF2200 is defined in the BIOS, with the current rule in matching_id(), this device will be regarded as a PNP device since there is WACFXXX in the acpi_pnp_device_ids[] and this PNP device is attached to the acpi device as the 1st physical_node, this will make the i2c bus match fail when i2c bus calls acpi_companion_match() to match the acpi_id_table in the i2c-hid driver. WACF2200 is an i2c device instead of a PNP device, after adding the string length comparing, the matching_id() will return false when matching WACF2200 and WACFXXX, and it is reasonable to compare the string length when matching two IDs. Suggested-by: Rafael J. Wysocki Signed-off-by: Hui Wang Cc: All applicable Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/acpi_pnp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/acpi/acpi_pnp.c b/drivers/acpi/acpi_pnp.c index f3039b93ff61a..101887528848d 100644 --- a/drivers/acpi/acpi_pnp.c +++ b/drivers/acpi/acpi_pnp.c @@ -317,6 +317,9 @@ static bool matching_id(const char *idstr, const char *list_id) { int i; + if (strlen(idstr) != strlen(list_id)) + return false; + if (memcmp(idstr, list_id, 3)) return false;