Re: [PATCH] usb: gadget: f_uvc: Expose configuration name through video node

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Wednesday, 23 May 2018 23:39:47 EEST Kieran Bingham wrote:
> From: Kieran Bingham 
> 
> When utilising multiple instantiations of a UVC gadget on a composite
> device, there is no clear method to link a particular configuration to
> its respective video node.
> 
> Provide a means for identifying the correct video node by exposing the
> name of the function configuration through sysfs.
> 
> Signed-off-by: Kieran Bingham 
> ---
>  drivers/usb/gadget/function/f_uvc.c | 24 +++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uvc.c
> b/drivers/usb/gadget/function/f_uvc.c index 1affa8e3a974..f326d1707633
> 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -421,10 +421,21 @@ uvc_function_disconnect(struct uvc_device *uvc)
>   * USB probe and disconnect
>   */
> 
> +static ssize_t config_show(struct device *dev, struct device_attribute
> *attr, + char *buf)
> +{
> + struct uvc_device *uvc = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%s\n", uvc->func.fi->group.cg_item.ci_name);
> +}
> +
> +static DEVICE_ATTR_RO(config);

You need to document the attribute in Documentation/ABI/.

I wonder whether we should use a more explicit name for the attribute. Maybe 
function_name ? usb_function_name ? usb_configfs_name ? Feel free to propose a 
better option.

> +
>  static int
>  uvc_register_video(struct uvc_device *uvc)
>  {
>   struct usb_composite_dev *cdev = uvc->func.config->cdev;
> + int ret;
> 
>   /* TODO reference counting. */
>   uvc->vdev.v4l2_dev = >v4l2_dev;
> @@ -437,7 +448,17 @@ uvc_register_video(struct uvc_device *uvc)
> 
>   video_set_drvdata(>vdev, uvc);
> 
> - return video_register_device(>vdev, VFL_TYPE_GRABBER, -1);
> + ret = video_register_device(>vdev, VFL_TYPE_GRABBER, -1);
> + if (ret < 0)
> + return ret;
> +
> + ret = device_create_file(>vdev.dev, _attr_config);
> + if (ret < 0) {
> + video_unregister_device(>vdev);
> + return ret;
> + }
> +
> + return 0;
>  }
> 
>  #define UVC_COPY_DESCRIPTOR(mem, dst, desc) \
> @@ -875,6 +896,7 @@ static void uvc_unbind(struct usb_configuration *c,
> struct usb_function *f)
> 
>   INFO(cdev, "%s\n", __func__);
> 
> + device_remove_file(>vdev.dev, _attr_config);
>   video_unregister_device(>vdev);
>   v4l2_device_unregister(>v4l2_dev);

-- 
Regards,

Laurent Pinchart



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[PATCH] usb: gadget: f_uvc: Expose configuration name through video node

[Kieran Bingham]

From: Kieran Bingham 

When utilising multiple instantiations of a UVC gadget on a composite
device, there is no clear method to link a particular configuration to
its respective video node.

Provide a means for identifying the correct video node by exposing the
name of the function configuration through sysfs.

Signed-off-by: Kieran Bingham 
---
 drivers/usb/gadget/function/f_uvc.c | 24 +++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c 
b/drivers/usb/gadget/function/f_uvc.c
index 1affa8e3a974..f326d1707633 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -421,10 +421,21 @@ uvc_function_disconnect(struct uvc_device *uvc)
  * USB probe and disconnect
  */
 
+static ssize_t config_show(struct device *dev, struct device_attribute *attr,
+  char *buf)
+{
+   struct uvc_device *uvc = dev_get_drvdata(dev);
+
+   return sprintf(buf, "%s\n", uvc->func.fi->group.cg_item.ci_name);
+}
+
+static DEVICE_ATTR_RO(config);
+
 static int
 uvc_register_video(struct uvc_device *uvc)
 {
struct usb_composite_dev *cdev = uvc->func.config->cdev;
+   int ret;
 
/* TODO reference counting. */
uvc->vdev.v4l2_dev = >v4l2_dev;
@@ -437,7 +448,17 @@ uvc_register_video(struct uvc_device *uvc)
 
video_set_drvdata(>vdev, uvc);
 
-   return video_register_device(>vdev, VFL_TYPE_GRABBER, -1);
+   ret = video_register_device(>vdev, VFL_TYPE_GRABBER, -1);
+   if (ret < 0)
+   return ret;
+
+   ret = device_create_file(>vdev.dev, _attr_config);
+   if (ret < 0) {
+   video_unregister_device(>vdev);
+   return ret;
+   }
+
+   return 0;
 }
 
 #define UVC_COPY_DESCRIPTOR(mem, dst, desc) \
@@ -875,6 +896,7 @@ static void uvc_unbind(struct usb_configuration *c, struct 
usb_function *f)
 
INFO(cdev, "%s\n", __func__);
 
+   device_remove_file(>vdev.dev, _attr_config);
video_unregister_device(>vdev);
v4l2_device_unregister(>v4l2_dev);
 
-- 
2.17.0

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