Hi, On Thu, Oct 09, 2014 at 03:21:51PM +0200, Robert Baldyga wrote: > Since we can compose gadgets from many functions, there is the problem > related to gadget breakage while FunctionFS daemon being closed. FFS > function is userspace code so there is no way to know when it will close > files (it doesn't matter what is the reason of this situation, it can > be daemon logic, program breakage, process kill or any other). So when > we have another function in gadget which, for example, sends some amount > of data, does some software update or implements some real-time functionality, > we may want to keep the gadget connected despite FFS function is no longer > functional. > > We can't just remove one of functions from gadget since it has been > enumerated, so the only way to keep entire gadget working is to make > broken FFS function deactivated but still visible to host. For this > purpose this patch introduces "no_disconnect" mode. It can be enabled > by setting mount option "no_disconnect=1", and results with defering > function disconnect to the moment of reopen ep0 file or filesystem > unmount. After closing all endpoint files, FunctionFS is set to state > FFS_DEACTIVATED. > > When ffs->state == FFS_DEACTIVATED: > - function is still bound and visible to host, > - setup requests are automatically stalled, > - transfers on other endpoints are refused, > - epfiles, except ep0, are deleted from the filesystem, > - opening ep0 causes the function to be closes, and then FunctionFS > is ready for descriptors and string write, > - unmounting of the FunctionFS instance causes the function to be closed. > > Signed-off-by: Robert Baldyga <[email protected]>
David, you have been messing with ffs lately, can I get a Tested-by from you on this patch ? > --- > > Changelog: > > v4: > - use ffs_data_reset() instead of ffs_data_clear() to reset ffs data > properly after ffs->ref refcount reach 0 (or under in no_disconnect > mode) in ffs_data_put() function > > v3: https://lkml.org/lkml/2014/10/9/170 > - change option name to more descriptive and less scary, > - fix cleaning up on unmount (call ffs_data_closed() in ffs_fs_kill_sb(), > and ffs_data_clear() in ffs_data_closed() if ffs->opened is negative). > > v2: https://lkml.org/lkml/2014/10/7/109 > - delete epfiles, excepting ep0, when FFS is in "zombie" mode, > - add description of FFS_ZOMBIE state, > - minor cleanups. > > v1: https://lkml.org/lkml/2014/10/6/128 > > drivers/usb/gadget/function/f_fs.c | 42 > +++++++++++++++++++++++++++++++------- > drivers/usb/gadget/function/u_fs.h | 22 ++++++++++++++++++++ > 2 files changed, 57 insertions(+), 7 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_fs.c > b/drivers/usb/gadget/function/f_fs.c > index 12dbdaf..2d47d4a 100644 > --- a/drivers/usb/gadget/function/f_fs.c > +++ b/drivers/usb/gadget/function/f_fs.c > @@ -606,6 +606,8 @@ static unsigned int ffs_ep0_poll(struct file *file, > poll_table *wait) > } > case FFS_CLOSING: > break; > + case FFS_DEACTIVATED: > + break; > } > > mutex_unlock(&ffs->mutex); > @@ -1152,6 +1154,7 @@ struct ffs_sb_fill_data { > struct ffs_file_perms perms; > umode_t root_mode; > const char *dev_name; > + bool no_disconnect; > struct ffs_data *ffs_data; > }; > > @@ -1222,6 +1225,12 @@ static int ffs_fs_parse_opts(struct ffs_sb_fill_data > *data, char *opts) > > /* Interpret option */ > switch (eq - opts) { > + case 13: > + if (!memcmp(opts, "no_disconnect", 13)) > + data->no_disconnect = !!value; > + else > + goto invalid; > + break; > case 5: > if (!memcmp(opts, "rmode", 5)) > data->root_mode = (value & 0555) | S_IFDIR; > @@ -1286,6 +1295,7 @@ ffs_fs_mount(struct file_system_type *t, int flags, > .gid = GLOBAL_ROOT_GID, > }, > .root_mode = S_IFDIR | 0500, > + .no_disconnect = false, > }; > struct dentry *rv; > int ret; > @@ -1302,6 +1312,7 @@ ffs_fs_mount(struct file_system_type *t, int flags, > if (unlikely(!ffs)) > return ERR_PTR(-ENOMEM); > ffs->file_perms = data.perms; > + ffs->no_disconnect = data.no_disconnect; > > ffs->dev_name = kstrdup(dev_name, GFP_KERNEL); > if (unlikely(!ffs->dev_name)) { > @@ -1333,6 +1344,7 @@ ffs_fs_kill_sb(struct super_block *sb) > kill_litter_super(sb); > if (sb->s_fs_info) { > ffs_release_dev(sb->s_fs_info); > + ffs_data_closed(sb->s_fs_info); > ffs_data_put(sb->s_fs_info); > } > } > @@ -1389,7 +1401,9 @@ static void ffs_data_opened(struct ffs_data *ffs) > ENTER(); > > atomic_inc(&ffs->ref); > - atomic_inc(&ffs->opened); > + if (atomic_add_return(1, &ffs->opened) == 1) > + if (ffs->state == FFS_DEACTIVATED) > + ffs_data_reset(ffs); > } > > static void ffs_data_put(struct ffs_data *ffs) > @@ -1411,9 +1425,22 @@ static void ffs_data_closed(struct ffs_data *ffs) > ENTER(); > > if (atomic_dec_and_test(&ffs->opened)) { > - ffs->state = FFS_CLOSING; > - ffs_data_reset(ffs); > + if (ffs->no_disconnect) { > + ffs->state = FFS_DEACTIVATED; > + if (ffs->epfiles) { > + ffs_epfiles_destroy(ffs->epfiles, > + ffs->eps_count); > + ffs->epfiles = NULL; > + } > + if (ffs->setup_state == FFS_SETUP_PENDING) > + __ffs_ep0_stall(ffs); > + } else { > + ffs->state = FFS_CLOSING; > + ffs_data_reset(ffs); > + } > } > + if (atomic_read(&ffs->opened) < 0) > + ffs_data_reset(ffs); > > ffs_data_put(ffs); > } > @@ -1588,7 +1615,6 @@ static void ffs_epfiles_destroy(struct ffs_epfile > *epfiles, unsigned count) > kfree(epfiles); > } > > - > static void ffs_func_eps_disable(struct ffs_function *func) > { > struct ffs_ep *ep = func->eps; > @@ -1601,10 +1627,12 @@ static void ffs_func_eps_disable(struct ffs_function > *func) > /* pending requests get nuked */ > if (likely(ep->ep)) > usb_ep_disable(ep->ep); > - epfile->ep = NULL; > - > ++ep; > - ++epfile; > + > + if (epfile) { > + epfile->ep = NULL; > + ++epfile; > + } > } while (--count); > spin_unlock_irqrestore(&func->ffs->eps_lock, flags); > } > diff --git a/drivers/usb/gadget/function/u_fs.h > b/drivers/usb/gadget/function/u_fs.h > index cd128e3..7bc0ca2 100644 > --- a/drivers/usb/gadget/function/u_fs.h > +++ b/drivers/usb/gadget/function/u_fs.h > @@ -93,6 +93,26 @@ enum ffs_state { > FFS_ACTIVE, > > /* > + * Function is visible to host, but it's not functional. All > + * setup requests are stalled and transfers on another endpoints > + * are refused. All epfiles, except ep0, are deleted so there > + * is no way to perform any operations on them. > + * > + * This state is set after closing all functionfs files, when > + * mount parameter "no_disconnect=1" has been set. Function will > + * remain in deactivated state until filesystem is umounted or > + * ep0 is opened again. In the second case functionfs state will > + * be reset, and it will be ready for descriptors and strings > + * writing. > + * > + * This is useful only when functionfs is composed to gadget > + * with another function which can perform some critical > + * operations, and it's strongly desired to have this operations > + * completed, even after functionfs files closure. > + */ > + FFS_DEACTIVATED, > + > + /* > * All endpoints have been closed. This state is also set if > * we encounter an unrecoverable error. The only > * unrecoverable error is situation when after reading strings > @@ -251,6 +271,8 @@ struct ffs_data { > kgid_t gid; > } file_perms; > > + bool no_disconnect; > + > /* > * The endpoint files, filled by ffs_epfiles_create(), > * destroyed by ffs_epfiles_destroy(). > -- > 1.9.1 > -- balbi
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