Re: [PATCH v3] Bluetooth: Fix registering hci with duplicate name

[Andrei Emeltchenko <andrei.emeltchenko.news@xxxxxxxxx>]

Hi Ulisses,

On Wed, Apr 18, 2012 at 12:13:04PM -0300, Ulisses Furquim wrote:
> When adding HCI devices hci_register_dev assigns the same name
> hci1 for subsequently added AMP devices.
> 
> ...
> [ 6958.381886] sysfs: cannot create duplicate filename
>        '/devices/virtual/bluetooth/hci1
> ...
> 
> We assume id starts with the number we'll try to add the new device
> and keep iterating until we find the proper place. The only difference
> is we start with 0 for BR/EDR device and 1 for AMP devices (thus AMP
> devices will never receive register as index 0). Then every hdev->id in
> the _ordered_ list <= to the id we want we increment id and move the
> variable head. In the end we'll have id as the first available one and
> head is where you need to add hdev after to keep the list ordered.
> 
> Reported-by: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
> Signed-off-by: Ulisses Furquim <ulisses@xxxxxxxxxxxxxx>
> ---
> 
> v3 - really add new hdev after head to keep the list ordered.
> v2 - only increment id when we find it's already there in the list.
> 
> ---
>  net/bluetooth/hci_core.c |   16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index c4dc263..2b98c33 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -1739,24 +1739,28 @@ int hci_le_scan(struct hci_dev *hdev, u8 type, u16 interval, u16 window,
>  /* Register HCI device */
>  int hci_register_dev(struct hci_dev *hdev)
>  {
> -	struct list_head *head = &hci_dev_list, *p;
> +	struct list_head *head, *p;
>  	int i, id, error;
>  
>  	if (!hdev->open || !hdev->close)
>  		return -EINVAL;
>  
> +	write_lock(&hci_dev_list_lock);
> +
>  	/* Do not allow HCI_AMP devices to register at index 0,
>  	 * so the index can be used as the AMP controller ID.
>  	 */
>  	id = (hdev->dev_type == HCI_BREDR) ? 0 : 1;
> -
> -	write_lock(&hci_dev_list_lock);
> +	head = &hci_dev_list;
>  
>  	/* Find first available device id */
>  	list_for_each(p, &hci_dev_list) {
> -		if (list_entry(p, struct hci_dev, list)->id != id)
> +		int nid = list_entry(p, struct hci_dev, list)->id;
> +		if (nid > id)
>  			break;
> -		head = p; id++;
> +		if (nid == id)
> +			id++;
> +		head = p;
>  	}

This looks to be working but I still prefer bitmask approach as it results
in simpler code like shown below:

<------8<------------------------------------------
|  list_for_each_entry(d, &hci_dev_list, list)
|          set_bit(d->id, inuse);
|
|  id = find_first_zero_bit(inuse, PAGE_SIZE * 8);
|
<------8<------------------------------------------

Anyway I leave it to maintainers to decide.

Tested-by: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx> 

Best regards 
Andrei Emeltchenko 

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