On Fri, 1 Apr 2016, Michal Nazarewicz wrote:
> On Thu, Mar 31 2016, Alan Stern wrote:
> > Michal, I'm not sure how you intended to handle this.
>
> For legacy/nokia setting no_configfs should be a valid solution:
>
> ---- >8 ----------------------------------------------------------------
> diff --git a/drivers/usb/gadget/legacy/nokia.c b/drivers/usb/gadget/legacy/nokia.c
> index 0997504..e4bc607 100644
> --- a/drivers/usb/gadget/legacy/nokia.c
> +++ b/drivers/usb/gadget/legacy/nokia.c
> @@ -223,6 +223,7 @@ static int nokia_bind_config(struct usb_configuration *c)
> }
>
> fsg_opts = fsg_opts_from_func_inst(fi_msg);
> + fsg_opts->no_configfs = true;
>
> status = fsg_common_run_thread(fsg_opts->common);
> if (status)
> ---- >8 ----------------------------------------------------------------
>
> This is what other legacy gadgets do after all.
Okay, that makes sense. Legacy gadgets aren't meant to be used with
configfs anyway.
> For configfs, why not simply check if the thread has already been
> started:
>
> ---- >8 ----------------------------------------------------------------
> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
> index acf210f..62854b6 100644
> --- a/drivers/usb/gadget/function/f_mass_storage.c
> +++ b/drivers/usb/gadget/function/f_mass_storage.c
> @@ -2984,8 +2984,10 @@ int fsg_common_run_thread(struct fsg_common *common)
> common->thread_task =
> kthread_create(fsg_main_thread, common, "file-storage");
> if (IS_ERR(common->thread_task)) {
> + int ret = PTR_ERR(common->thread_task);
> + common->thread_task = NULL;
> common->state = FSG_STATE_TERMINATED;
> - return PTR_ERR(common->thread_task);
> + return ret;
> }
>
> DBG(common, "I/O thread pid: %d\n", task_pid_nr(common->thread_task));
> @@ -3005,6 +3007,7 @@ static void fsg_common_release(struct kref *ref)
> if (common->state != FSG_STATE_TERMINATED) {
> raise_exception(common, FSG_STATE_EXIT);
> wait_for_completion(&common->thread_notifier);
> + common->thread_task = NULL;
> }
>
> for (i = 0; i < ARRAY_SIZE(common->luns); ++i) {
> @@ -3050,9 +3053,11 @@ static int fsg_bind(struct usb_configuration *c, struct usb_function *f)
> if (ret)
> return ret;
> fsg_common_set_inquiry_string(fsg->common, NULL, NULL);
> - ret = fsg_common_run_thread(fsg->common);
> - if (ret)
> - return ret;
> + if (common->thread_task) {
Do you mean: if (!common->thread_task)?
> + ret = fsg_common_run_thread(fsg->common);
> + if (ret)
> + return ret;
> + }
> }
>
> fsg->gadget = gadget;
> ---- >8 ----------------------------------------------------------------
>
> With that, the whole fsg_common_run_thread call should be moved outside
> of the if (!no_configfs) and legacy should no longer call it IMO.
I'm not so sure about this. Earlier I was undecided about what to do
if there are multiple mass-storage interfaces in the same config, but
now I realize that one thread won't work in that situation. The
difficulty is exception handling. If an error occurs in one of the
interfaces, it shouldn't affect the others -- but with only one thread
you can't make that work.
I don't know the details of how the composite core works (I don't even
remember the difference between a usb_function and a
usb_function_instance). Suppose there are several interfaces in one
config, each bound to the mass-storage driver. Then won't the driver's
bind routine get called several times whenever the config is installed?
If so, then each of those calls should create a new thread. There's no
need to check if the thread has already been started.
If not, then there's no way to use f_mass_storage on multiple
interfaces in a single config. The driver should refuse to run on more
than one interface at a time.
Alan Stern
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