[PATCH] usb: atm: cxacru: Zero initialize bp in cxacru_heavy_init()

[Nathan Chancellor <nathan@kernel.org>]

After a recent change in clang to expose uninitialized warnings from
const variables [1], there is a warning in cxacru_heavy_init():

  drivers/usb/atm/cxacru.c:1104:6: error: variable 'bp' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
   1104 |         if (instance->modem_type->boot_rom_patch) {
        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  drivers/usb/atm/cxacru.c:1113:39: note: uninitialized use occurs here
   1113 |         cxacru_upload_firmware(instance, fw, bp);
        |                                              ^~
  drivers/usb/atm/cxacru.c:1104:2: note: remove the 'if' if its condition is always true
   1104 |         if (instance->modem_type->boot_rom_patch) {
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  drivers/usb/atm/cxacru.c:1095:32: note: initialize the variable 'bp' to silence this warning
   1095 |         const struct firmware *fw, *bp;
        |                                       ^
        |                                        = NULL

This warning occurs in clang's frontend before inlining occurs, so it
cannot notice that bp is only used within cxacru_upload_firmware() under
the same condition that initializes it in cxacru_heavy_init(). Just
initialize bp to NULL to silence the warning without functionally
changing the code, which is what happens with modern compilers when they
support '-ftrivial-auto-var-init=zero' (CONFIG_INIT_STACK_ALL_ZERO=y).

Cc: stable@vger.kernel.org
Fixes: 1b0e61465234 ("[PATCH] USB ATM: driver for the Conexant AccessRunner chipset cxacru")
Closes: https://github.com/ClangBuiltLinux/linux/issues/2102
Link: https://github.com/llvm/llvm-project/commit/2464313eef01c5b1edf0eccf57a32cdee01472c7 [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/usb/atm/cxacru.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/atm/cxacru.c b/drivers/usb/atm/cxacru.c
index a12ab90b3db7..b7c3b224a759 100644
--- a/drivers/usb/atm/cxacru.c
+++ b/drivers/usb/atm/cxacru.c
@@ -1092,7 +1092,7 @@ static int cxacru_find_firmware(struct cxacru_data *instance,
 static int cxacru_heavy_init(struct usbatm_data *usbatm_instance,
 			     struct usb_interface *usb_intf)
 {
-	const struct firmware *fw, *bp;
+	const struct firmware *fw, *bp = NULL;
 	struct cxacru_data *instance = usbatm_instance->driver_data;
 	int ret = cxacru_find_firmware(instance, "fw", &fw);
 

---
base-commit: fdfa018c6962c86d2faa183187669569be4d513f
change-id: 20250715-usb-cxacru-fix-clang-21-uninit-warning-9430d96c6bc1

Best regards,
--  
Nathan Chancellor <nathan@kernel.org>