Re: [PATCH v2] USB: gadget: Add ID numbers to configfs-gadget driver names

[Chanh Nguyen]

On 22/12/2022 22:20, Andrzej Pietrasiewicz wrote:
> Hi,
>
> W dniu 21.12.2022 o 10:13, Chanh Nguyen pisze:
> > 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
>
> I assume you are interested in a scenario where there is more than one
> UDC available which means you can have more than one active gadget?

Yes, I'd like to have more active gadgets. For example, mass_storage and 
ecm usb, ...

> > 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@xxxxxxxxxxxxxxxxxxxxxx>
> >
> > ---
> > Changes in v2:
> >    - Replace scnprintf() by kasprintf() to simplify the code [CJ]
> >    - Move the clean up code from gadgets_drop() to
> >      gadget_info_attr_release()                        [Frank Li]
> >    - Correct the resource free up in gadges_make()   [Alan Stern]
> >    - Remove the unnecessary variable in gadgets_make()    [Chanh]
> >    - Fixes minor grammar issue in commit message          [Chanh]
> > ---
> >   drivers/usb/gadget/configfs.c | 25 ++++++++++++++++++++++++-
> >   1 file changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/gadget/configfs.c 
> > b/drivers/usb/gadget/configfs.c
> > index 96121d1c8df4..7faf68bfa716 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 +12,8 @@
> >   #include "u_f.h"
> >   #include "u_os_desc.h"
> > +static DEFINE_IDA(driver_id_numbers);
> > +
> >   int check_user_usb_string(const char *name,
> >           struct usb_gadget_strings *stringtab_dev)
> >   {
> > @@ -52,6 +55,9 @@ 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)
> > @@ -393,6 +399,8 @@ static void gadget_info_attr_release(struct 
> > config_item *item)
> >       WARN_ON(!list_empty(&gi->string_list));
> >       WARN_ON(!list_empty(&gi->available_func));
> >       kfree(gi->composite.gadget_driver.function);
> > +    kfree(gi->composite.gadget_driver.driver.name);
> > +    ida_free(&driver_id_numbers, gi->driver_id_number);
> >       kfree(gi);
> >   }
> > @@ -1623,13 +1631,28 @@ 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);
>
> I'm wondering if it maybe makes more sense to use the gadget name as a 
> suffix
> instead?
>
>      gi->composite.gadget_driver.driver.name =
>          kasprintf(GFP_KERNEL, "configfs-gadget.%s" name);
>
> So that when you
>
> mkdir g1
>
> you will ultimately see /sys/bus/gadget/drivers/configfs-gadget.g1
>
> instead of /sys/bus/gadget/drivers/configfs-gadget.0
>
> Gadget names are guaranteed to be unique because they are created
> as sibling subdirectories in configfs. Your patch would then be greatly
> simplified (no need for ida).
>
> Regards,
>
> Andrzej

Thanks, Andrzej! I'll update that in patch v3

> > +    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_name;
> >       return &gi->group;
> > +
> > +out_free_driver_name:
> > +    kfree(gi->composite.gadget_driver.driver.name);
> > +out_free_driver_id_number:
> > +    ida_free(&driver_id_numbers, gi->driver_id_number);
> >   err:
> >       kfree(gi);
> >       return ERR_PTR(-ENOMEM);