On Sat, Apr 09, 2022 at 11:57:56AM +0300, Maxim Devaev wrote:
> В Fri, 8 Apr 2022 10:59:45 -0400
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > > At least there is one situation where the behavior of f_mass_storage differs
> > > from the behavior of a real drive. What happens when you click on the physical
> > > "eject" button?
> >
> > If the host has prevented ejection, nothing happens. Otherwise the disc
> > gets ejected.
> >
> > > Yes, the OS can block this, but the problem is that we don't have
> > > an "eject" here.
> >
> > What do you mean? Writing an empty string to the sysfs "file" attribute
> > is the virtual analog of pressing the eject button.
>
> But I can't eject the disc event it's not mounted on Linux host. It seems to me
> it differs from the real drive behavior.
It sounds like either there's a bug or else you're not doing the right
thing. Tell me exactly what you do when this fails.
> > ...
>
> I have reflected on the rest of your arguments and changed my mind.
> I think that "forced_eject" for a specific lun without interrupting operations would
> really be the best solution. I wrote a simple patch and tested it, everything seems
> to work. What do you think about something like this?
>
>
> static ssize_t fsg_lun_opts_forced_eject_store(struct config_item *item,
> const char *page, size_t len)
> {
> struct fsg_lun_opts *opts = to_fsg_lun_opts(item);
> struct fsg_opts *fsg_opts = to_fsg_opts(opts->group.cg_item.ci_parent);
> int ret;
>
> opts->lun->prevent_medium_removal = 0;
> ret = fsg_store_file(opts->lun, &fsg_opts->common->filesem, "", 0);
> return ret < 0 ? ret : len;
> }
>
> CONFIGFS_ATTR_WO(fsg_lun_opts_, forced_eject);
The basic idea is right. But this should not be a CONFIGFS option; it
should be an ordinary LUN attribute. For an example, see the definition of
file_store() in f_mass_storage.c; your routine should look very similar.
> If you find this acceptable, I will test this patch on my users to make sure
> that its behavior meets our expectations.
Okay.
Alan Stern
