Re: Juju
From: Kristian HÃgsberg
Date: Fri Jan 26 2007 - 14:58:07 EST
Greg KH wrote:
On Thu, Jan 25, 2007 at 03:38:24PM -0800, Pete Zaitcev wrote:
On Thu, 25 Jan 2007 16:18:35 -0500, Kristian H??gsberg <krh@xxxxxxxxxx> wrote:
I see that ORBs are always allocated with a call (like SKB) and not
embedded into drivers (like URBs). It's great, keep it up. Also,
never allow drivers to pass DMA-mapped buffers into fw_send_request
and friends. We made both of these mistakes in USB, and it hurts.
Oh, the ORBs are SBP-2 specific data structures, struct fw_transaction is
probably what corresponds to USB URBs. This struct is defined in
fw-transaction.h and is available for embedding into other structs, such as
struct sbp2_orb in fw-sbp2. Is that what you're suggesting against, and what
are the problems with this approach?
Fortunately we do not care about out-of-tree drivers, which are most
affected, you may even call it a feature ^_^. My main problem is,
we can't refcount URBs, so usbmon can't tap them and must copy.
urbs are reference counted, it's just that not all drivers who create
them use them that way :(
Perhaps you can inforce this in the new codebase...
It's a small change to make the fw_transaction struct opaque and ref-counted,
and it's definitely still doable. But the nice thing about embedding the
struct is that you have one memory allocation failure path less to worry
about. And I haven't yet, and don't expect to see a use case that will need
ref-counted struct fw_transaction, the ownership is always clearly defined.
But I can go either way on this and if there is a good reason to ref count
them it's a pretty small change.
cheers,
Kristian
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