>>>>> "Andrzej" == Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx> writes:
> Hi Peter,
> W dniu 18.01.2024 o 15:48, Peter Korsgaard pisze:
>> When a USB gadget is configured through configfs with 1 or more f_fs
>> functions, then the logic setting up the gadget configuration has to wait
>> until the user space code (typically separate applications) responsible for
>> those functions have written their descriptors before the gadget can be
>> activated.
>> The f_fs instance already knows if this has been done, so expose it
>> through
>> a "ready" attribute in configfs for easier synchronization.
>> Signed-off-by: Peter Korsgaard <peter@xxxxxxxxxxxxx>
>> ---
>> Changes since v2:
>> - Add ABI documentation as requested by Greg
>> Changes since v1:
>> - Add documentation snippet as requested by Greg.
>> Documentation/ABI/testing/configfs-usb-gadget-ffs | 12
>> ++++++++++--
>> Documentation/usb/gadget-testing.rst | 8 ++++++++
>> drivers/usb/gadget/function/f_fs.c | 15 +++++++++++++++
>> 3 files changed, 33 insertions(+), 2 deletions(-)
>> diff --git a/Documentation/ABI/testing/configfs-usb-gadget-ffs
>> b/Documentation/ABI/testing/configfs-usb-gadget-ffs
>> index e39b27653c65..bf8936ff6d38 100644
>> --- a/Documentation/ABI/testing/configfs-usb-gadget-ffs
>> +++ b/Documentation/ABI/testing/configfs-usb-gadget-ffs
>> @@ -4,6 +4,14 @@ KernelVersion: 3.13
>> Description: The purpose of this directory is to create and remove it.
>> A corresponding USB function instance is
>> created/removed.
>> - There are no attributes here.
>> - All parameters are set through FunctionFS.
>> + All attributes are read only:
>> +
>> + ============= ============================================
>> + ready 1 if the function is ready to be used, E.G.
>> + if userspace has written descriptors and
>> + strings to ep0, so the gadget can be
>> + enabled - 0 otherwise.
>> + ============= ============================================
>> +
>> + All other parameters are set through FunctionFS.
>> diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
>> index 29072c166d23..fcbd8bb22db4 100644
>> --- a/Documentation/usb/gadget-testing.rst
>> +++ b/Documentation/usb/gadget-testing.rst
>> @@ -206,6 +206,14 @@ the standard procedure for using FunctionFS (mount it, run the userspace
>> process which implements the function proper). The gadget should be enabled
>> by writing a suitable string to usb_gadget/<gadget>/UDC.
>> +The FFS function provides just one attribute in its function
>> directory:
>> +
>> + ready
>> +
>> +The attribute is read-only and signals if the function is ready (1) to be
>> +used, E.G. if userspace has written descriptors and strings to ep0, so
>> +the gadget can be enabled.
>> +
>> Testing the FFS function
>> ------------------------
>> diff --git a/drivers/usb/gadget/function/f_fs.c
>> b/drivers/usb/gadget/function/f_fs.c
>> index fdd0fc7b8f25..ae44dd5f3a94 100644
>> --- a/drivers/usb/gadget/function/f_fs.c
>> +++ b/drivers/usb/gadget/function/f_fs.c
>> @@ -3446,6 +3446,20 @@ static inline struct f_fs_opts *to_ffs_opts(struct config_item *item)
>> func_inst.group);
>> }
>> +static ssize_t f_fs_opts_ready_show(struct config_item *item,
>> char *page)
>> +{
>> + struct f_fs_opts *opts = to_ffs_opts(item);
>> +
>> + return sprintf(page, "%d\n", opts->dev->desc_ready);
> Don't we need some locking here? "desc_ready" seems to be manipulated
> always under ffs_dev_lock().
Ups, indeed. It is just a boolean, but the instance could disappear from
under us.
I'll send an update, thanks.
--
Bye, Peter Korsgaard
