Re: [PATCH] USB: gadget: Add ID numbers to configfs-gadget driver names

[Chanh Nguyen <chanh@amperemail.onmicrosoft.com>]

On 13/12/2022 14:22, Christophe JAILLET wrote:
> Le 13/12/2022 à 05:12, Chanh Nguyen a écrit :
>> It is unable to use configfs to attach more than one gadget. When
>> attaching the second gadget, it always fails and the kernel message
>> prints out:
>>
>> Error: Driver 'configfs-gadget' is already registered, aborting...
>> UDC core: g1: driver registration failed: -16
>>
>> This commit fixes the problem by a ".N" suffix added to each
>> configfs_gadget's driver name (where N is a unique ID number),
>> thus making the names distinct.
>>
>> Fixes: fc274c1e9973 ("USB: gadget: Add a new bus for gadgets")
>> Signed-off-by: Chanh Nguyen 
>> <chanh-shex6MNQR2J/SfDzf78azzKzEDxYleXD@public.gmane.org>
>> ---
>>   drivers/usb/gadget/configfs.c | 42 +++++++++++++++++++++++++++++++++++
>>   1 file changed, 42 insertions(+)
>>
>> diff --git a/drivers/usb/gadget/configfs.c 
>> b/drivers/usb/gadget/configfs.c
>> index 96121d1c8df4..d8c5156ad777 100644
>> --- a/drivers/usb/gadget/configfs.c
>> +++ b/drivers/usb/gadget/configfs.c
>> @@ -3,6 +3,7 @@
>>   #include <linux/module.h>
>>   #include <linux/slab.h>
>>   #include <linux/device.h>
>> +#include <linux/idr.h>
>>   #include <linux/kstrtox.h>
>>   #include <linux/nls.h>
>>   #include <linux/usb/composite.h>
>> @@ -11,6 +12,16 @@
>>   #include "u_f.h"
>>   #include "u_os_desc.h"
>> +static DEFINE_IDA(driver_id_numbers);
>> +
>> +/*
>> + * Driver name has the form of "configfs-gadget.%d", where %d
>> + * is id allocated by ida_alloc(). The max value returns by
>> + * ida_alloc() is INT_MAX, in 64-bit system, it is about nine
>> + * quintillion: 19 digits in decimal. Set the max length to 35.
>> + */
>> +#define DRIVER_NAME_LENGTH_MAX 35
> 
> Hi,
> 
> if paranoiac, the final \0 seems to be missing in the max length 
> computation, but see below.

Thanks CJ! Indeed, I have missed that.

> 
>> +
>>   int check_user_usb_string(const char *name,
>>           struct usb_gadget_strings *stringtab_dev)
>>   {
>> @@ -52,6 +63,9 @@ struct gadget_info {
>>       char qw_sign[OS_STRING_QW_SIGN_LEN];
>>       spinlock_t spinlock;
>>       bool unbind;
>> +
>> +    /* Make driver names unique */
>> +    int driver_id_number;
>>   };
>>   static inline struct gadget_info *to_gadget_info(struct config_item 
>> *item)
>> @@ -1582,6 +1596,8 @@ static struct config_group *gadgets_make(
>>           const char *name)
>>   {
>>       struct gadget_info *gi;
>> +    char *driver_name;
>> +    int ret;
>>       gi = kzalloc(sizeof(*gi), GFP_KERNEL);
>>       if (!gi)
>> @@ -1623,6 +1639,21 @@ static struct config_group *gadgets_make(
>>       gi->composite.gadget_driver = configfs_driver_template;
>> +    ret = ida_alloc(&driver_id_numbers, GFP_KERNEL);
>> +    if (ret < 0)
>> +        goto err;
>> +    gi->driver_id_number = ret;
>> +
>> +    driver_name = kmalloc(DRIVER_NAME_LENGTH_MAX, GFP_KERNEL);
>> +    if (!driver_name)
>> +        goto out_free_driver_id_number;
>> +
>> +    ret = scnprintf(driver_name, DRIVER_NAME_LENGTH_MAX,
>> +            "configfs-gadget.%d", gi->driver_id_number);
> 
> 
> using kasprintf() looks simpler here.
> No need to kmalloc()+scnprintf(), and no need for DRIVER_NAME_LENGTH_MAX.
> 
> Just my 2c,
> 
> CJ

Thanks CJ for the review!

I've made some changes as below (in gadgets_make() to remove unnecessary 
variables) and now trying to test it as much as possible. Will re-post 
it as v2 if looks good soon.

static inline struct gadget_info *to_gadget_info(struct config_item *item)
@@ -1623,13 +1629,25 @@ static struct config_group *gadgets_make(

      gi->composite.gadget_driver = configfs_driver_template;

+    gi->driver_id_number = ida_alloc(&driver_id_numbers, GFP_KERNEL);
+    if (gi->driver_id_number < 0)
+        goto err;
+
+    gi->composite.gadget_driver.driver.name =
+                          kasprintf(GFP_KERNEL, "configfs-gadget.%d",
+                                    gi->driver_id_number);
+    if (!gi->composite.gadget_driver.driver.name)
+        goto out_free_driver_id_number;
+
      gi->composite.gadget_driver.function = kstrdup(name, GFP_KERNEL);
      gi->composite.name = gi->composite.gadget_driver.function;

      if (!gi->composite.gadget_driver.function)
-        goto err;
+        goto out_free_driver_id_number;

      return &gi->group;
+
+out_free_driver_id_number:
+    ida_free(&driver_id_numbers, gi->driver_id_number);
  err:
      kfree(gi);
      return ERR_PTR(-ENOMEM);


> 
>> +    if (ret < 0)
>> +        goto out_free_driver_name;
>> +
>> +    gi->composite.gadget_driver.driver.name = driver_name;
>>       gi->composite.gadget_driver.function = kstrdup(name, GFP_KERNEL);
>>       gi->composite.name = gi->composite.gadget_driver.function;
>> @@ -1630,6 +1661,11 @@ static struct config_group *gadgets_make(
>>           goto err;
>>       return &gi->group;
>> +
>> +out_free_driver_name:
>> +    kfree(driver_name);
>> +out_free_driver_id_number:
>> +    ida_free(&driver_id_numbers, gi->driver_id_number);
>>   err:
>>       kfree(gi);
>>       return ERR_PTR(-ENOMEM);
>> @@ -1637,6 +1673,12 @@ static struct config_group *gadgets_make(
>>   static void gadgets_drop(struct config_group *group, struct 
>> config_item *item)
>>   {
>> +    struct gadget_info *gi = to_gadget_info(item);
>> +
>> +    mutex_lock(&gi->lock);
>> +    kfree(gi->composite.gadget_driver.driver.name);
>> +    ida_free(&driver_id_numbers, gi->driver_id_number);
>> +    mutex_unlock(&gi->lock);
>>       config_item_put(item);
>>   }
>