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

On Mon, 21 Nov 2016 12:52:47 +0100, Andrej Kruták wrote:

On Mon, Nov 21, 2016 at 11:47 AM, Takashi Iwai tiwai@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@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