In the export_store function, the error handling paths followed a
successful vinput_alloc_vdevice call are missing a corresponding
input_free_device call. Since vinput_alloc_vdevice internally calls
input_allocate_device, and input_register_device has not been called
yet, input_free_device should be used to properly free the allocated
input_device struct in this scenario[1].
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/input.c#n2094
In the export_store function, when vinput_register_vdevice fails, the
current error handling process calls device_unregister followed by
vinput_destroy_vdevice. However, the device_unregister here triggers its
release function, which already includes a call to
vinput_destroy_vdevice. As a result, vinput_destroy_vdevice is called
twice. Since vinput_destroy_vdevice contains module_put, this double
call must be avoided to prevent potential reference count issues.
After class_register failure, the wrong function class_unregister was
used. The correct cleanup function should be unregister_chrdev, as
register_chrdev was used before class_register.
When raw_copy_to_user() failed in vinput_read(), the function would set
'count' to -EFAULT and then subtract EFAULT from '*offset'. However,
modifying '*offset' on raw_copy_to_user() failure was incorrect. Fix
this behavior by changing count = -EFAULT to return -EFAULT.
When kzalloc fails to allocate memory and returns NULL, it leads to a
NULL pointer dereference error later on. Add a check for the return
value of kzalloc. When kzalloc fails to allocate memory, it prints an
error message and returns ERR_PTR(-ENOMEM).
The description of the attribute was added in sysfs section and referenced in vinput section.
In vinput section, just described the class_attribute and some macros about sysfs class.
Add file name at vinput-related examples begin.
