Re: [PATCH] usb: optimize set_bulk_out_req_length() in mass storage gadgets

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Hi,

On Tue, Oct 04, 2011 at 10:44:36AM -0700, Paul Zimmerman wrote:
> > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] 
> > Sent: Tuesday, October 04, 2011 6:57 AM
> > 
> > On Mon, 3 Oct 2011, Paul Zimmerman wrote:
> > 
> > > Since bulk max packet size must always be a power of 2, we can
> > > use the 'and' operator instead of modulus.
> > 
> > Just a quick observation: AFAIK, in wireless USB the bulk maxpacket
> > size does not have to be a power of 2.  On the other hand, if it isn't
> > then it's not clear that the mass-storage gadgets would work.
> 
> Drat, I forgot about WUSB and it's dreaded non-power-of-2 max packet
> sizes.
> 
> I guess it's better not to apply the patch then, it's probably only
> a tiny optimization on any halfway modern CPU.

that would mean that for dwc3, we would need to use a chained transfer
for the remaining bytes, right ? Meaning that we would need a 1024bytes
throw-away buffer for that, correct ?

I'll start playing with that tomorrow and see how that could be done...
I guess I could get that finished by v3.3

-- 
balbi

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