| Message ID | 20230307232636.9369-1-Jerry@skydio.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | usb: gadget: f_fs: Send a create event for endpoint files | expand |
<resend as your email headers were corrupt so only got sent to 1 person> On Tue, Mar 07, 2023 at 03:26:36PM -0800, Jerry Zhang wrote: > From: Jerry Zhang <jerry@skydio.com> > > If userspace is creating a composite gadget with one or > more functionfs functions, it generally goes through a process of: > > 1. mount functionfs devices > 2. start up driver processes > 3. driver processes open ep0 and write descriptors > 4. once all descriptors are written, enable gadget > > The user may want the gadget to be enabled as soon as possible. > However there is no race-free way to know when to enable the gadget > since the gadget enable process doesn't know the status of the > other driver processes. Furthermore, other driver processes > may be fixed binaries, so there may not be an opportunity to > modify their source to use a cooperative synchronization method. > > This can be resolved by enabling inotify create events for endpoint > files. The gadget enable process can create inotify watches in each > driver's directory, and a create event for "ep1" will indicate that > the driver has finished writing descriptors. Once events for all > drivers have been received, the gadget is ready to be enabled. > > Signed-off-by: Jerry Zhang <jerry@skydio.com> > --- > drivers/usb/gadget/function/f_fs.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c > index ddfc537c7526..fc038db46e14 100644 > --- a/drivers/usb/gadget/function/f_fs.c > +++ b/drivers/usb/gadget/function/f_fs.c > @@ -13,10 +13,11 @@ > > /* #define DEBUG */ > /* #define VERBOSE_DEBUG */ > > #include <linux/blkdev.h> > +#include <linux/fsnotify.h> > #include <linux/pagemap.h> > #include <linux/export.h> > #include <linux/fs_parser.h> > #include <linux/hid.h> > #include <linux/mm.h> > @@ -1443,10 +1444,11 @@ static struct dentry *ffs_sb_create_file(struct super_block *sb, > dput(dentry); > return NULL; > } > > d_add(dentry, inode); > + fsnotify_create(dentry->d_parent->d_inode, dentry); > return dentry; > } > > /* Super block */ > static const struct super_operations ffs_sb_operations = { > -- > 2.37.3 > This is a good idea, but where is it now documented that this is the expected functionality and that userspace can rely on this? thanks, greg k-h
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index ddfc537c7526..fc038db46e14 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -13,10 +13,11 @@ /* #define DEBUG */ /* #define VERBOSE_DEBUG */ #include <linux/blkdev.h> +#include <linux/fsnotify.h> #include <linux/pagemap.h> #include <linux/export.h> #include <linux/fs_parser.h> #include <linux/hid.h> #include <linux/mm.h> @@ -1443,10 +1444,11 @@ static struct dentry *ffs_sb_create_file(struct super_block *sb, dput(dentry); return NULL; } d_add(dentry, inode); + fsnotify_create(dentry->d_parent->d_inode, dentry); return dentry; } /* Super block */ static const struct super_operations ffs_sb_operations = {