[PATCH v2] usb: gadget: f_uac1_legacy: remove broken string configfs attributes

[Xu Yang <xu.yang_2@oss.nxp.com>]

From: Xu Yang <xu.yang_2@nxp.com>

The UAC1_STR_ATTRIBUTE macro defines configfs show/store handlers for
the fn_play, fn_cap, and fn_cntl string options. The store function
contains an inverted null check on the kstrndup() return value.

This means every write attempt returns -ENOMEM on success and
dereferences a NULL pointer on allocation failure. The attributes
have been broken and unused for many years.

Remove the UAC1_STR_ATTRIBUTE macro and the three attributes it
generated. The internal defaults (FILE_PCM_PLAYBACK, FILE_PCM_CAPTURE,
FILE_CONTROL) set in f_audio_alloc_inst() are unaffected.

Fixes: 0854611a19ae ("usb: gadget: f_uac1: add configfs support")
Link: https://lore.kernel.org/linux-usb/20260625113154.1954813-1-xu.yang_2@oss.nxp.com/
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Assisted-by: Claude:claude-sonnet-4.6
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

---
Changes in v2:
 - Remove fn_play, fn_cap, and fn_cntl in gadget-testing.rst
 - Remove fn_*_alloc variable
---
 .../testing/configfs-usb-gadget-uac1_legacy   |  3 -
 Documentation/usb/gadget-testing.rst          |  3 -
 drivers/usb/gadget/function/f_uac1_legacy.c   | 56 -------------------
 drivers/usb/gadget/function/u_uac1_legacy.h   |  3 -
 4 files changed, 65 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uac1_legacy b/Documentation/ABI/testing/configfs-usb-gadget-uac1_legacy
index b2eaefd9bc49..6a681d219f43 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uac1_legacy
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uac1_legacy
@@ -5,8 +5,5 @@ Description:
 		The attributes:
 
 		audio_buf_size - audio buffer size
-		fn_cap - capture pcm device file name
-		fn_cntl - control device file name
-		fn_play - playback pcm device file name
 		req_buf_size - ISO OUT endpoint request buffer size
 		req_count - ISO OUT endpoint request count
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index a6e8292f320a..4921e5307d49 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -714,9 +714,6 @@ The uac1 function provides these attributes in its function directory:
 
 	=============== ====================================
 	audio_buf_size	audio buffer size
-	fn_cap		capture pcm device file name
-	fn_cntl		control device file name
-	fn_play		playback pcm device file name
 	req_buf_size	ISO OUT endpoint request buffer size
 	req_count	ISO OUT endpoint request count
 	=============== ====================================
diff --git a/drivers/usb/gadget/function/f_uac1_legacy.c b/drivers/usb/gadget/function/f_uac1_legacy.c
index 5d201a2e30e7..3f52099a4fdd 100644
--- a/drivers/usb/gadget/function/f_uac1_legacy.c
+++ b/drivers/usb/gadget/function/f_uac1_legacy.c
@@ -888,60 +888,10 @@ UAC1_INT_ATTRIBUTE(req_buf_size);
 UAC1_INT_ATTRIBUTE(req_count);
 UAC1_INT_ATTRIBUTE(audio_buf_size);
 
-#define UAC1_STR_ATTRIBUTE(name)					\
-static ssize_t f_uac1_opts_##name##_show(struct config_item *item,	\
-					 char *page)			\
-{									\
-	struct f_uac1_legacy_opts *opts = to_f_uac1_opts(item);		\
-	int result;							\
-									\
-	mutex_lock(&opts->lock);					\
-	result = sprintf(page, "%s\n", opts->name);			\
-	mutex_unlock(&opts->lock);					\
-									\
-	return result;							\
-}									\
-									\
-static ssize_t f_uac1_opts_##name##_store(struct config_item *item,	\
-					  const char *page, size_t len)	\
-{									\
-	struct f_uac1_legacy_opts *opts = to_f_uac1_opts(item);		\
-	int ret = -EBUSY;						\
-	char *tmp;							\
-									\
-	mutex_lock(&opts->lock);					\
-	if (opts->refcnt)						\
-		goto end;						\
-									\
-	tmp = kstrndup(page, len, GFP_KERNEL);				\
-	if (tmp) {							\
-		ret = -ENOMEM;						\
-		goto end;						\
-	}								\
-	if (opts->name##_alloc)						\
-		kfree(opts->name);					\
-	opts->name##_alloc = true;					\
-	opts->name = tmp;						\
-	ret = len;							\
-									\
-end:									\
-	mutex_unlock(&opts->lock);					\
-	return ret;							\
-}									\
-									\
-CONFIGFS_ATTR(f_uac1_opts_, name)
-
-UAC1_STR_ATTRIBUTE(fn_play);
-UAC1_STR_ATTRIBUTE(fn_cap);
-UAC1_STR_ATTRIBUTE(fn_cntl);
-
 static struct configfs_attribute *f_uac1_attrs[] = {
 	&f_uac1_opts_attr_req_buf_size,
 	&f_uac1_opts_attr_req_count,
 	&f_uac1_opts_attr_audio_buf_size,
-	&f_uac1_opts_attr_fn_play,
-	&f_uac1_opts_attr_fn_cap,
-	&f_uac1_opts_attr_fn_cntl,
 	NULL,
 };
 
@@ -956,12 +906,6 @@ static void f_audio_free_inst(struct usb_function_instance *f)
 	struct f_uac1_legacy_opts *opts;
 
 	opts = container_of(f, struct f_uac1_legacy_opts, func_inst);
-	if (opts->fn_play_alloc)
-		kfree(opts->fn_play);
-	if (opts->fn_cap_alloc)
-		kfree(opts->fn_cap);
-	if (opts->fn_cntl_alloc)
-		kfree(opts->fn_cntl);
 	kfree(opts);
 }
 
diff --git a/drivers/usb/gadget/function/u_uac1_legacy.h b/drivers/usb/gadget/function/u_uac1_legacy.h
index b5df9bcbbeba..b9ddae550ff3 100644
--- a/drivers/usb/gadget/function/u_uac1_legacy.h
+++ b/drivers/usb/gadget/function/u_uac1_legacy.h
@@ -62,9 +62,6 @@ struct f_uac1_legacy_opts {
 	char				*fn_cap;
 	char				*fn_cntl;
 	unsigned			bound:1;
-	unsigned			fn_play_alloc:1;
-	unsigned			fn_cap_alloc:1;
-	unsigned			fn_cntl_alloc:1;
 	struct mutex			lock;
 	int				refcnt;
 };
-- 
2.34.1