Re: [PATCH v2] usb: dwc3: handle DWC_USB3_NUM == DWC_USB3_NUM_IN_EPS

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, 23 Jan 2017, John Youn wrote:

> On 1/22/2017 5:29 PM, Bryan O'Donoghue wrote:
> > - DWC_USB3_NUM indicates the number of Device mode single directional
> >   endpoints, including OUT and IN endpoint 0.
> >
> > - DWC_USB3_NUM_IN_EPS indicates the maximum number of Device mode IN
> >   endpoints active at any time, including control endpoint 0.
> >
> > It's possible to configure RTL such that DWC_USB3_NUM_EPS is equal to
> > DWC_USB3_NUM_IN_EPS.
> >
> > dwc3-core calculates the number of OUT endpoints as DWC_USB3_NUM minus
> > DWC_USB3_NUM_IN_EPS. If RTL has been configured with DWC_USB3_NUM_IN_EPS
> > equal to DWC_USB3_NUM then dwc3-core will calculate the number of OUT
> > endpoints as zero.
> >
> > For example a from dwc3_core_num_eps() shows:
> > [    1.565000]  /usb0@f01d0000: found 8 IN and 0 OUT endpoints
> >
> > This patch works around this case by detecting when DWC_USB3_NUM_EPS is
> > equal to DWC3_USB3_NUM_IN_EPS and over-rides the calculation of the number
> 
> What if NUM_IN_EPS=7 and NUM_EPS=8? You will still have a problem.
> 
> It's possible to fix this for the general case rather than for this
> specific case.

What is the reason for computing NUM_OUT_EPS in the first place?  
Isn't it true that any endpoint can be used as an OUT endpoint?

So the real restrictions on a configuration are:

	number of IN endpoints <= NUM_IN_EPS, and

	number of IN endpoints + number of OUT endpoints <= NUM_EPS,

where ep0 must be counted twice, as both an IN and an OUT endpoint.  
The value of NUM_OUT_EPS isn't used and shouldn't matter.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux