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

[Chanh Nguyen]

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@xxxxxxxxxxxxxxxx>
> > ---
> >   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);
> >   }