On 1/23/2023 11:33 AM, Thinh Nguyen wrote:
On Sat, Jan 21, 2023, Thinh Nguyen wrote:
On Fri, Jan 20, 2023, Alan Stern wrote:
On Sat, Jan 21, 2023 at 02:02:36AM +0000, Thinh Nguyen wrote:
On Fri, Jan 20, 2023, Alan Stern wrote:
A UDC design might have multiple versions, some supporting remote wakeup
and others not. But drivers generally use a single static
usb_gadget_ops structure, and they don't modify it at runtime to account
for hardware differences. So if a single driver controls those multiple
versions, you can't rely on the presence of gadget->ops->wakeup to
indicate whether there actually is hardware remote wakeup support.
Ideally, the usb_gadget structure should have a wakeup_capable flag
which the UDC driver would set appropriately (probably during its probe
routine).
I was thinking that it can be handled by the
usb_gadget_enable_remote_wakeup() so we can do away with the
wakeup_capable flag.
usb_gadget_enable_remote_wakeup() gets called when the gadget or
function is suspended, right? But a gadget driver may want to know long
before that whether the UDC supports remote wakeup, in order to set up
its config descriptor correctly.
No, this is to be called during set configuration. If the configuration
doesn't support remote wakeup, the device should not be able to send
remote wakeup.
On second thought, you're right about the descriptor. It's better to
warn and prevent the remote wakeup bit from being set in the descriptor
if the UDC doesn't support remote wakeup. Warning the user at set
configuration is too late.
So, we need both rw_capable flag and usb_gadget_enable_remote_wakeup().
Thanks,
Thinh
Do we need usb_gadget_enable_remote_wakeup() gadget-op ?
As per the discussion, we can have rw_capable flag in usb_gadget struct
and set it during gagdet init/probe if the UDC supports resume
signalling OR wants the remote wakeup feature to be enabled.
This flag now represents UDC capability to initiate resume signalling.
During enumeration phase, when preparing the config descriptor we can
use gadget->rw_capable flag to rightly modify the remote wakeup
bit. Based on this, host will decide whether to arm the device for
remote wakeup or not.
For gadget->ops->wakeup callback support we already have explicit checks
when invoking this gadget op and device wont be able to send remote
wakeup if callback support doesn't exist.
Please let me know if I am missing something.
Thanks
Elson
