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usb: gadget: uvc: configfs: Add interface number attributes

PATCH New Laurent Pinchart 1 participant 1 message Aug 1, 2018 USB

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Laurent Pinchart

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PATCH 4/8 usb: gadget: uvc: configfs: Add interface number attributes

Hi Kieran,

Quoted 13 lines · On Wednesday, 1 August 2018 13:07:20 EEST Kieran Bingham wrote:
Quoted 12 lines · Laurent Pinchart

The video control and video streaming interface numbers are needed in the UVC gadget userspace stack to reply to UVC requests. They are hardcoded to fixed values at the moment, preventing configurations with multiple functions.

To fix this, make them dynamically discoverable by userspace through read-only configfs attributes in <function>/control/bInterfaceNumber and <function>/streaming/bInterfaceNumber respectively.

Signed-off-by Laurent Pinchart <[email protected]>

---

Quoted 7 lines
Quoted 3 lines
 drivers/usb/gadget/function/f_uvc.c        |  2 +
 drivers/usb/gadget/function/u_uvc.h        |  3 ++
 drivers/usb/gadget/function/uvc_configfs.c | 62 +++++++++++++++++++++++++

It sounds like this is extending the userspace ABI.

Do we need to document this anywhere?
Documentation/ABI/testing/configfs-usb-gadget-uvc ?

You're right, I'll document it.

Quoted 1 line
Quoted 1 line
 3 files changed, 67 insertions(+)

[snip]

Quoted 39 lines
Quoted 39 lines
(quoted diff) +0 -0

b/drivers/usb/gadget/function/uvc_configfs.c index e019ea317c7a..801117686108 100644

drivers/usb/gadget/function/uvc_configfs.c +0 -0
@@ -687,8 +687,39 @@ static const struct uvcg_config_group_type

uvcg_control_class_grp_type = {>
* control
*/

drivers/usb/gadget/function/uvc_configfs.c +29 -0
+static ssize_t uvcg_default_control_b_interface_number_show(
+	struct config_item *item, char *page)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	int result = 0;
+
+	mutex_lock(su_mutex); /* for navigating configfs hierarchy */
+
+	opts_item = item->ci_parent;
+	opts = to_f_uvc_opts(opts_item);
+
+	mutex_lock(&opts->lock);
+	result += sprintf(page, "%u\n", opts->control_interface);
+	mutex_unlock(&opts->lock);
+
+	mutex_unlock(su_mutex);
+
+	return result;
+}
+
+UVC_ATTR_RO(uvcg_default_control_, b_interface_number, bInterfaceNumber);
+
+static struct configfs_attribute *uvcg_default_control_attrs[] = {
+	&uvcg_default_control_attr_b_interface_number,
+	NULL,
+};

[snip]

Quoted 26 lines
Quoted 12 lines
drivers/usb/gadget/function/uvc_configfs.c +12 -0
+static ssize_t uvcg_default_streaming_b_interface_number_show(
+	struct config_item *item, char *page)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	int result = 0;
+
+	mutex_lock(su_mutex); /* for navigating configfs hierarchy */
+
+	opts_item = item->ci_parent;

drivers/usb/gadget/function/uvc_configfs.c

Quoted 10 lines
drivers/usb/gadget/function/uvc_configfs.c +10 -0
+	opts = to_f_uvc_opts(opts_item);
+
+	mutex_lock(&opts->lock);
+	result += sprintf(page, "%u\n", opts->streaming_interface);
+	mutex_unlock(&opts->lock);
+
+	mutex_unlock(su_mutex);
+
+	return result;
+}

That looks like a lot of common boilerplate code copied for each file which prints a single %u.

Quoted 1 line

Perhaps we should convert those to a macro - but for now they look fine.

Feel free to submit patches :-) Helper functions would be event better than macros to decrease the object size.

Quoted 8 lines
Quoted 8 lines
drivers/usb/gadget/function/uvc_configfs.c +2 -0
+
+UVC_ATTR_RO(uvcg_default_streaming_, b_interface_number,

bInterfaceNumber);
+static struct configfs_attribute
*uvcg_default_streaming_attrs[] = {

drivers/usb/gadget/function/uvc_configfs.c +3 -0
+	&uvcg_default_streaming_attr_b_interface_number,
+	NULL,
+};

[snip]