Re: [PATCH 0/4] USB: fix runtime PM after driver unbind

[Johan Hovold <johan@kernel.org>]

On Mon, Sep 30, 2019 at 01:36:03PM -0300, Mauro Carvalho Chehab wrote:
> Em Mon, 30 Sep 2019 18:12:01 +0200
> Johan Hovold <johan@kernel.org> escreveu:
> 
> > A recent change in USB core broke runtime-PM after driver unbind in
> > several drivers (when counting all USB serial drivers). Specifically,
> > drivers which took care not modify the runtime-PM usage counter after
> > their disconnect callback had returned, would now fail to be suspended
> > when a driver is later bound.
> > 
> > I guess Greg could take all of these directly through his tree, unless
> > the media maintainers disagree.
> 
> Patches look ok and I'm fine if they go via Greg's tree. So:
> 
> Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Thanks for taking a look.

> Yet, on a quick look on media:
> 
> 	$ git grep -l usb_.*pm drivers/media/usb/
> 	drivers/media/usb/cpia2/cpia2_usb.c
> 	drivers/media/usb/dvb-usb-v2/az6007.c
> 	drivers/media/usb/dvb-usb-v2/dvb_usb.h
> 	drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
> 	drivers/media/usb/gspca/gspca.c
> 	drivers/media/usb/gspca/gspca.h
> 	drivers/media/usb/siano/smsusb.c
> 	drivers/media/usb/stkwebcam/stk-webcam.c
> 	drivers/media/usb/usbvision/usbvision-i2c.c
> 	drivers/media/usb/uvc/uvc_driver.c
> 	drivers/media/usb/uvc/uvc_v4l2.c
> 	drivers/media/usb/zr364xx/zr364xx.c
> 
> There are other drivers beside stkwebcam with has some PM routines.

Yeah, but that may be for system-wide suspend.

> Ok, only two (stkwebcam and uvcvideo) uses usb_autopm_get_interface() and
> usb_autopm_put_interface(), but I'm wondering if the others are doing the
> right thing, as their implementation are probably older.

Right, only these two support runtime PM through USB core (autosuspend).

In fact, I see now that stkwebcam fails to set the supports_autosuspend
flag in its usb_driver struct, so runtime PM has never actually been
enabled for this driver either. But I guess it doesn't hurt to fix
missing puts if someones wants to try enabling it, if not only for
documentation purposes and avoiding copy-paste proliferation.

Lots of legacy...

Johan