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

> 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@os.amperecomputing.com>
>
> ---
> 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

> + 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);

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