Re: [PATCH 02/12] Bluetooth: Add basic start/complete HCI transaction functions

[Johan Hedberg <johan.hedberg@gmail.com>]

Hi Andre,

On Thu, Feb 14, 2013, Andre Guedes wrote:
> > +int hci_start_transaction(struct hci_dev *hdev)
> > +{
> > +       struct hci_transaction *transaction;
> > +       int err;
> > +
> > +       hci_transaction_lock(hdev);
> > +
> > +       /* We can't start a new transaction if there's another one in
> > +        * progress of being built.
> > +        */
> > +       if (hdev->build_transaction) {
> > +               err = -EBUSY;
> > +               goto unlock;
> > +       }
> > +
> > +       transaction = kmalloc(sizeof(*transaction), GFP_ATOMIC);
> 
> I've failed to see why we need GFP_ATOMIC here. As this code is not
> running in any atomic section, we can allocate memory using
> GFP_KERNEL.

Since one of the intentions of this API is to create an async version of
hci_request() I think it's better to keep GFP_ATOMIC here. One situation
where you couldn't for sure use hci_request() is if you're in an atomic
section and then a HCI request would be the only other alternative.

> > +       if (!transaction) {
> > +               err = -ENOMEM;
> > +               goto unlock;
> > +       }
> > +
> > +       memset(transaction, 0, sizeof(*transaction));
> 
> We can also use kzalloc instead of kmalloc, making this memset unnecessary.

Good point. Fixed in v2.

Johan