classmate-laptop: should check for NULL as retval for rfkill_alloc

rfkill_alloc returns NULL when it fails if RFKILL is enabled. When RFKILL is
disabled, its return value of ERR_PTR(-ENODEV) is OK to use as all rfkill
functions will work with it, as they are simply empty stubs.

Reported-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: platform-driver-x86@vger.kernel.org
Cc: mjg@redhat.com
Cc: don@syst.com.br
Cc: rpurdie@rpsys.net
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/platform/x86/classmate-laptop.c b/drivers/platform/x86/classmate-laptop.c
index 3bf399fe2bb..73ea76e6f21 100644
--- a/drivers/platform/x86/classmate-laptop.c
+++ b/drivers/platform/x86/classmate-laptop.c
@@ -573,16 +573,17 @@ static int cmpc_ipml_add(struct acpi_device *acpi)
 
         ipml->rf = rfkill_alloc("cmpc_rfkill", &acpi->dev, RFKILL_TYPE_WLAN,
                                 &cmpc_rfkill_ops, acpi->handle);
-        /* rfkill_alloc may fail if RFKILL is disabled. We should still work
-         * anyway. */
-        if (!IS_ERR(ipml->rf)) {
+        /*
+         * If RFKILL is disabled, rfkill_alloc will return ERR_PTR(-ENODEV).
+         * This is OK, however, since all other uses of the device will not
+         * derefence it.
+         */
+        if (ipml->rf) {
                 retval = rfkill_register(ipml->rf);
                 if (retval) {
                         rfkill_destroy(ipml->rf);
                         ipml->rf = NULL;
                 }
-        } else {
-                ipml->rf = NULL;
         }
 
         dev_set_drvdata(&acpi->dev, ipml);