[alsa-devel] [PATCH] ALSA: line6: Claim POD X3 USB data interface

[Takashi Iwai]

On Mon, 21 Nov 2016 12:52:47 +0100,
Andrej Kruták wrote:
> 
> On Mon, Nov 21, 2016 at 11:47 AM, Takashi Iwai <tiwai at suse.de> wrote:
> > On Sat, 19 Nov 2016 13:01:29 +0100,
> > Andrej Krutak wrote:
> >>
> >> Deny userspace from using the interface concurrently.
> >
> > Could you clarify more what's wrong and what you're changing?
> >
> >
> 
> Userspace apps have to claim USB interfaces before using endpoints in
> them (drivers/usb/core/devio.c:checkintf()). It's a lock mechanism so
> that two "drivers"
> don't steal data from each other. Kernel drivers don't necessarily
> have to claim interfaces (obviously, because it worked so far) - but
> they should, to lock out userspace...
> 
> Do you want that info in a v2 patch?

Sure, such vital information must be given to the patch.


thanks,

Takashi

> 
> >>
> >> Signed-off-by: Andrej Krutak <dev at andree.sk>
> >> ---
> >>  sound/usb/line6/driver.h |  1 +
> >>  sound/usb/line6/podhd.c  | 24 ++++++++++++++++++++++++
> >>  2 files changed, 25 insertions(+)
> >>
> >> diff --git a/sound/usb/line6/driver.h b/sound/usb/line6/driver.h
> >> index 7e3a3aa..5d18957 100644
> >> --- a/sound/usb/line6/driver.h
> >> +++ b/sound/usb/line6/driver.h
> >> @@ -98,6 +98,7 @@ struct line6_properties {
> >>
> >>       int altsetting;
> >>
> >> +     unsigned ctrl_if;
> >>       unsigned ep_ctrl_r;
> >>       unsigned ep_ctrl_w;
> >>       unsigned ep_audio_r;
> >> diff --git a/sound/usb/line6/podhd.c b/sound/usb/line6/podhd.c
> >> index 49cd4a6..6c53b87 100644
> >> --- a/sound/usb/line6/podhd.c
> >> +++ b/sound/usb/line6/podhd.c
> >> @@ -153,6 +153,7 @@ struct usb_line6_podhd {
> >>                           .rats = &podhd_ratden},
> >>       .bytes_per_channel = 3 /* SNDRV_PCM_FMTBIT_S24_3LE */
> >>  };
> >> +static struct usb_driver podhd_driver;
> >>
> >>  static void podhd_startup_start_workqueue(unsigned long data);
> >>  static void podhd_startup_workqueue(struct work_struct *work);
> >> @@ -291,8 +292,13 @@ static void podhd_disconnect(struct usb_line6 *line6)
> >>       struct usb_line6_podhd *pod = (struct usb_line6_podhd *)line6;
> >>
> >>       if (pod->line6.properties->capabilities & LINE6_CAP_CONTROL) {
> >> +             struct usb_interface *intf;
> >> +
> >>               del_timer_sync(&pod->startup_timer);
> >>               cancel_work_sync(&pod->startup_work);
> >> +
> >> +             intf = usb_ifnum_to_if(line6->usbdev, pod->line6.properties->ctrl_if);
> >> +             usb_driver_release_interface(&podhd_driver, intf);
> >>       }
> >>  }
> >>
> >> @@ -304,10 +310,26 @@ static int podhd_init(struct usb_line6 *line6,
> >>  {
> >>       int err;
> >>       struct usb_line6_podhd *pod = (struct usb_line6_podhd *) line6;
> >> +     struct usb_interface *intf;
> >>
> >>       line6->disconnect = podhd_disconnect;
> >>
> >>       if (pod->line6.properties->capabilities & LINE6_CAP_CONTROL) {
> >> +             /* claim the data interface */
> >> +             intf = usb_ifnum_to_if(line6->usbdev, pod->line6.properties->ctrl_if);
> >> +             if (!intf) {
> >> +                     dev_err(pod->line6.ifcdev, "interface %d not found\n",
> >> +                             pod->line6.properties->ctrl_if);
> >> +                     return -ENODEV;
> >> +             }
> >> +
> >> +             err = usb_driver_claim_interface(&podhd_driver, intf, NULL);
> >> +             if (err != 0) {
> >> +                     dev_err(pod->line6.ifcdev, "can't claim interface %d, error %d\n",
> >> +                             pod->line6.properties->ctrl_if, err);
> >> +                     return err;
> >> +             }
> >> +
> >>               /* create sysfs entries: */
> >>               err = snd_card_add_dev_attr(line6->card, &podhd_dev_attr_group);
> >>               if (err < 0)
> >> @@ -406,6 +428,7 @@ static int podhd_init(struct usb_line6 *line6,
> >>               .altsetting = 1,
> >>               .ep_ctrl_r = 0x81,
> >>               .ep_ctrl_w = 0x01,
> >> +             .ctrl_if = 1,
> >>               .ep_audio_r = 0x86,
> >>               .ep_audio_w = 0x02,
> >>       },
> >> @@ -417,6 +440,7 @@ static int podhd_init(struct usb_line6 *line6,
> >>               .altsetting = 1,
> >>               .ep_ctrl_r = 0x81,
> >>               .ep_ctrl_w = 0x01,
> >> +             .ctrl_if = 1,
> >>               .ep_audio_r = 0x86,
> >>               .ep_audio_w = 0x02,
> >>       },
> >> --
> >> 1.9.1
> >>
> >>
>