Hi,
Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> writes:
> Hi Felipe,
> On Tue, 2019-05-28 at 11:11 +0300, Felipe Balbi wrote:
>> Hi,
>>
>> Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> writes:
>> > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
>> > index 7fcb9f782931..88b3ee03a12d 100644
>> > --- a/drivers/usb/core/usb.c
>> > +++ b/drivers/usb/core/usb.c
>> > @@ -1190,7 +1190,7 @@ EXPORT_SYMBOL_GPL(usb_debug_root);
>> >
>> > static void usb_debugfs_init(void)
>> > {
>> > - usb_debug_root = debugfs_create_dir("usb", NULL);
>> > + usb_debug_root = debugfs_create_dir(USB_DEBUG_ROOT_NAME, NULL);
>> > debugfs_create_file("devices", 0444, usb_debug_root, NULL,
>> > &usbfs_devices_fops);
>> > }
>>
>> might be a better idea to move this to usb common. Then have a function
>> which can be called by both host and gadget to maybe create the
>> directory:
>>
>> static struct dentry *usb_debug_root;
>>
>> struct dentry *usb_debugfs_init(void)
>> {
>> if (!usb_debug_root)
>> usb_debug_root = debugfs_create_dir("usb", NULL);
>>
>> return usb_debug_root;
>> }
>>
>>
>> Then usb core would be updated to something like:
>>
>> static void usb_core_debugfs_init(void)
>> {
>> struct dentry *root = usb_debugfs_init();
>>
>> debugfs_create_file("devices", 0444, root, NULL, &usbfs_devices_fops);
>> }
>>
> I find a problem when move usb_debugfs_init() and usb_debugfs_cleanup()
> into usb common, it's easy to create "usb" directory, but difficult to
> cleanup it:
>
> common/common.c
>
> struct dentry *usb_debugfs_init(void)
> {
> if (!usb_debug_root)
> usb_debug_root = debugfs_create_dir("usb", NULL);
>
> return usb_debug_root;
> }
>
> void usb_debugfs_cleanup(void)
> {
> debugfs_remove_recursive(usb_debug_root);
> usb_debug_root = NULL;
> }
>
> core/usb.c
>
> static void usb_core_debugfs_init(void)
> {
> struct dentry *root = usb_debugfs_init();
>
> debugfs_create_file("devices", 0444, root, NULL,
> &usbfs_devices_fops);
> }
>
> static int __init usb_init(void)
> {
> ...
> usb_core_debugfs_init();
> ...
> }
>
> static void __exit usb_exit(void)
> {
> ...
> usb_debugfs_cleanup();
> // will be error, gadget may use it.
> ...
> }
>
> gadget/udc/core.c
>
> static int __init usb_udc_init(void)
> {
> ...
> usb_debugfs_init();
> ...
> }
>
> static void __exit usb_udc_exit(void)
> {
> ...
> usb_debugfs_cleanup();
> // can't cleanup in fact, usb core may use it.
> }
>
> How to handle this case? introduce a reference count? do you have any
> suggestion?
I guess a simple refcount is the way to go:
struct dentry *usb_debugfs_init(void)
{
if (!usb_debug_root)
usb_debug_root = debugfs_create_dir("usb", NULL);
usb_debug_root_refcnt++;
return usb_debug_root;
}
void usb_debugfs_cleanup(void)
{
if (!(--usb_debug_root_refcnt)) {
debugfs_remove_recursive(usb_debug_root);
usb_debug_root = NULL;
}
}
Or something along those lines
--
balbi
