Messages in this thread | | | Date | Wed, 12 Nov 2014 17:03:18 -0500 (EST) | From | Alan Stern <> | Subject | Re: [V2 PATCH 01/10] added media agnostic (MA) USB HCD driver |
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On Wed, 12 Nov 2014, Sean O. Stalley wrote:
> On Tue, Nov 11, 2014 at 10:54:30AM -0500, Alan Stern wrote: > > On Mon, 10 Nov 2014, Stephanie Wallick wrote: > > > > > +static struct mausb_hcd mhcd; > > > > Only one statically-allocated structure? What if somebody wants to > > have more than one of these things in their system? > > > > Our plan to support multiple MA devices is to have them all connected > to the same virtual host controller, so only 1 would be needed. > > Would you prefer we have 1 host controller instance per MA device? > We are definitely open to suggestions on how this should be architected.
I haven't read the MA USB spec, so I don't know how it's intended to work. Still, what happens if you create a virtual host controller with, say, 16 ports, and then someone wants to connect a 17th MA device?
Also, I noticed that your patch adds a new bus type for these MA host controllers. It really seems like overkill to have a whole new bus type if there's only going to be one device on it.
> If we get rid of these locks, endpoints can't run simultaneously. > MA USB IN endpoints have to copy data, which could take a while.
I don't know what you mean by "run simultaneously". Certainly multiple network packets can be transmitted and received concurrently even if you use a single spinlock, since your locking won't affect the networking subsystem.
> Couldn't this cause a bottleneck?
Probably not enough to matter. After all, the other host controller drivers rely on a single spinlock. And if it did matter, you could drop the spinlock while copying the data.
Alan Stern
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