[alsa-devel] [PATCH v2] ALSA: line6: Claim POD X3 USB data interface

[Andrej Krutak]

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
have to claim interfaces to work - but they should, to lock out userspace...

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