Hi Alan,
On Sun, Mar 20, 2022 at 03:51:04PM -0400, Alan Stern wrote:
> This patch adds a "gadget" bus and uses it for registering gadgets and
> their drivers. From now on, bindings will be managed by the driver
> core rather than through ad-hoc manipulations in the UDC core.
>
> As part of this change, the driver_pending_list is removed. The UDC
> core won't need to keep track of unbound drivers for later binding,
> because the driver core handles all of that for us.
>
> However, we do need one new feature: a way to prevent gadget drivers
> from being bound to more than one gadget at a time. The existing code
> does this automatically, but the driver core doesn't -- it's perfectly
> happy to bind a single driver to all the matching devices on the bus.
> The patch adds a new bitflag to the usb_gadget_driver structure for
> this purpose.
>
> A nice side effect of this change is a reduction in the total lines of
> code, since now the driver core will do part of the work that the UDC
> used to do.
>
> A possible future patch could add udc devices to the gadget bus, say
> as a separate device type.
Can you please elaborate on this? This UDC device will be added to gadget bus
but not bound to any driver, correct?
>
> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> ---
>
> drivers/usb/gadget/udc/core.c | 248 +++++++++++++++++++-----------------------
> include/linux/usb/gadget.h | 26 ++--
> 2 files changed, 135 insertions(+), 139 deletions(-)
>
<snip>
>
> /* ------------------------------------------------------------------------- */
>
> -static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *driver)
> +static int gadget_match_driver(struct device *dev, struct device_driver *drv)
> {
> - int ret;
> + struct usb_gadget *gadget = dev_to_usb_gadget(dev);
> + struct usb_udc *udc = gadget->udc;
> + struct usb_gadget_driver *driver = container_of(drv,
> + struct usb_gadget_driver, driver);
>
> - dev_dbg(&udc->dev, "registering UDC driver [%s]\n",
> - driver->function);
> + /* If the driver specifies a udc_name, it must match the UDC's name */
> + if (driver->udc_name &&
> + strcmp(driver->udc_name, dev_name(&udc->dev)) != 0)
> + return 0;
>
> + /* Otherwise any gadget driver matches any UDC */
> + return 1;
> +}
> +
Would it be better if we add the driver->is_bound check here so that probe is
not invoked? your patch checks it later at the probe.
Thanks,
Pavan
