usb: gadget: uvc: Make bmControls attr read/write

For the Processing Unit and Camera Terminal descriptors defined in
the UVC Gadget we currently hard-code values into their bmControls
fields, which enumerates which controls the gadget is able to
support. This isn't appropriate since only the userspace companion
program to the kernel driver will know which controls are supported.
Make the configfs attributes that point to those fields read/write
so userspace can set them to appropriate values.

Document the new behaviour at the same time so the functionality is
clear.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230309105825.216745-1-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 119 insertions, 2 deletions

diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 62b759bb7613..9bf0e985acfa 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -334,6 +334,64 @@ UVCG_DEFAULT_PROCESSING_ATTR(i_processing, iProcessing, 8);
 
 #undef UVCG_DEFAULT_PROCESSING_ATTR
 
+static ssize_t uvcg_default_processing_bm_controls_store(
+	struct config_item *item, const char *page, size_t len)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct uvc_processing_unit_descriptor *pd;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	u8 *bm_controls, *tmp;
+	unsigned int i;
+	int ret, n = 0;
+
+	mutex_lock(su_mutex);
+
+	opts_item = group->cg_item.ci_parent->ci_parent->ci_parent;
+	opts = to_f_uvc_opts(opts_item);
+	pd = &opts->uvc_processing;
+
+	mutex_lock(&opts->lock);
+	if (opts->refcnt) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_count_item_entries, &n,
+				       sizeof(u8));
+	if (ret)
+		goto unlock;
+
+	if (n > pd->bControlSize) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	tmp = bm_controls = kcalloc(n, sizeof(u8), GFP_KERNEL);
+	if (!bm_controls) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_fill_item_entries, &tmp,
+				       sizeof(u8));
+	if (ret)
+		goto free_mem;
+
+	for (i = 0; i < n; i++)
+		pd->bmControls[i] = bm_controls[i];
+
+	ret = len;
+
+free_mem:
+	kfree(bm_controls);
+unlock:
+	mutex_unlock(&opts->lock);
+	mutex_unlock(su_mutex);
+	return ret;
+}
+
 static ssize_t uvcg_default_processing_bm_controls_show(
 	struct config_item *item, char *page)
 {
@@ -363,7 +421,7 @@ static ssize_t uvcg_default_processing_bm_controls_show(
 	return result;
 }
 
-UVC_ATTR_RO(uvcg_default_processing_, bm_controls, bmControls);
+UVC_ATTR(uvcg_default_processing_, bm_controls, bmControls);
 
 static struct configfs_attribute *uvcg_default_processing_attrs[] = {
 	&uvcg_default_processing_attr_b_unit_id,
@@ -445,6 +503,65 @@ UVCG_DEFAULT_CAMERA_ATTR(w_ocular_focal_length, wOcularFocalLength,
 
 #undef UVCG_DEFAULT_CAMERA_ATTR
 
+static ssize_t uvcg_default_camera_bm_controls_store(
+	struct config_item *item, const char *page, size_t len)
+{
+	struct config_group *group = to_config_group(item);
+	struct mutex *su_mutex = &group->cg_subsys->su_mutex;
+	struct uvc_camera_terminal_descriptor *cd;
+	struct config_item *opts_item;
+	struct f_uvc_opts *opts;
+	u8 *bm_controls, *tmp;
+	unsigned int i;
+	int ret, n = 0;
+
+	mutex_lock(su_mutex);
+
+	opts_item = group->cg_item.ci_parent->ci_parent->ci_parent->
+			ci_parent;
+	opts = to_f_uvc_opts(opts_item);
+	cd = &opts->uvc_camera_terminal;
+
+	mutex_lock(&opts->lock);
+	if (opts->refcnt) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_count_item_entries, &n,
+				       sizeof(u8));
+	if (ret)
+		goto unlock;
+
+	if (n > cd->bControlSize) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	tmp = bm_controls = kcalloc(n, sizeof(u8), GFP_KERNEL);
+	if (!bm_controls) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	ret = __uvcg_iter_item_entries(page, len, __uvcg_fill_item_entries, &tmp,
+				       sizeof(u8));
+	if (ret)
+		goto free_mem;
+
+	for (i = 0; i < n; i++)
+		cd->bmControls[i] = bm_controls[i];
+
+	ret = len;
+
+free_mem:
+	kfree(bm_controls);
+unlock:
+	mutex_unlock(&opts->lock);
+	mutex_unlock(su_mutex);
+	return ret;
+}
+
 static ssize_t uvcg_default_camera_bm_controls_show(
 	struct config_item *item, char *page)
 {
@@ -474,7 +591,7 @@ static ssize_t uvcg_default_camera_bm_controls_show(
 	return result;
 }
 
-UVC_ATTR_RO(uvcg_default_camera_, bm_controls, bmControls);
+UVC_ATTR(uvcg_default_camera_, bm_controls, bmControls);
 
 static struct configfs_attribute *uvcg_default_camera_attrs[] = {
 	&uvcg_default_camera_attr_b_terminal_id,