[Linux-gpib-general] Patch: do not use gpiod_put on GPIOs that were not allocated with gpiod_get (fixes crash on module unload on kernel 6.6)

[Michael S. <mi...@sc...>]

Hi,

I noticed crashes when unloading the gpib_bitbang module after upgrading my
development raspberry pi to kernel 6.6.  I traced them to the use of
gpiod_put on GPIO objects that were not allocated using gpiod_get, which
according to the ernel documentation should not be done.

The attached patch fixes the problem for me.

cu
Michael Schwingen



>From cb23c0aa14effc437041c39eb24178ca5f11e74c Mon Sep 17 00:00:00 2001
From: Michael Schwingen <mi...@sc...>
Date: Fri, 12 Jul 2024 16:35:08 +0200
Subject: [PATCH 1/2] do not use gpiod_put on GPIOs that were not allocated
 with gpiod_get (fixes crash on module unload on kernel 6.6)

---
 linux-gpib-kernel/drivers/gpib/gpio/gpib_bitbang.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/linux-gpib-kernel/drivers/gpib/gpio/gpib_bitbang.c b/linux-gpib-kernel/drivers/gpib/gpio/gpib_bitbang.c
index 5d5a2690..7aebf119 100644
--- a/linux-gpib-kernel/drivers/gpib/gpio/gpib_bitbang.c
+++ b/linux-gpib-kernel/drivers/gpib/gpio/gpib_bitbang.c
@@ -971,7 +971,6 @@ static int allocate_gpios(void) {
         if ( j != last) {                    /* error - undo what already done */
                 dbg_printk (0, "request for gpios failed at %d.\n", j);
                 while (j) {
-                        gpiod_put(all_descriptors[--j]);
                         all_descriptors[j] = 0;
                         gpio_free (gpios_vector[j]+gpio_offset);
                 }
@@ -985,7 +984,6 @@ static void release_gpios(void) {
         int j = sn7516x ? GPIB_PINS + SN7516X_PINS : GPIB_PINS ;
         while (j) {
                 if (all_descriptors[--j]) {
-                        gpiod_put(all_descriptors[j]);
                         all_descriptors[j] = 0;
                         gpio_free (gpios_vector[j]+gpio_offset);
                 }
@@ -1144,7 +1142,6 @@ static int __init bb_init_module(void)
 static void __exit bb_exit_module(void)
 {
 	gpiod_direction_input(ACT_LED);
-        gpiod_put(ACT_LED);
 
         dbg_printk(1,"%s\n", "module unloaded!");
 
-- 
2.39.2