On Wed, 2019-06-05 at 11:41 +0200, Greg KH wrote: > On Fri, May 10, 2019 at 11:01:09AM +0100, Mayuresh Kulkarni wrote: > > > > - The current driver increments the PM ref-count in its .open > > API and decrements it in its .close API. > > - Due to this, it is not possible for the usb_device to go into > > suspend (L2) even if all of its interfaces report idle to usb-core. > > - In order to allow the suspend, 2 new ioctls are added: > > 1. USBDEVFS_SUSPEND: calls auto-suspend and indicates to usb/pm core > > to attempt suspend, if appropriate. This is a non-blocking call. > > 2. USBDEVFS_WAIT_RESUME: waits for resume. This is a blocking call. > > The resume could happen due to: > > host-wake (i.e.: any driver bound to interface(s) of device wants to > > send/receive control/data) > > OR > > remote-wake (i.e.: when remote-wake enabled device generates a > > remote-wake to host). > > In both these conditions, this call will return. > > - It is expected that: > > 1. When user-space thinks the device is idle from its point-of-view, > > it calls USBDEVFS_SUSPEND. > > 2. After USBDEVFS_WAIT_RESUME call returns, > > the callers queries the device/interface of its interest to see > > what caused resume and take appropriate action on it. > I'm going to make a bunch of random comments on this patch, some > cosmetic... > Hi Greg, Apologies for late response from me. I was on PTO last week and then in a training this week. Thanks for your comments. I will fix most of them in next patch as Alan has suggested some more code-changes (in the later response than this one). > First off, the above is horrible to try to read, please format things in > a sane way such that we can understand it well. > > > > > The link to relevant discussion about this patch on linux-usb is - > > https://www.spinics.net/lists/linux-usb/msg173285.html > You should not need to reference any external web site for a changelog > entry, just put the needed information in the changelog itself. > > > > > Signed-off-by: Mayuresh Kulkarni <mkulkarni@xxxxxxxxxxxxxxxxxxxxx> > > --- > > drivers/usb/core/devio.c | 114 > > ++++++++++++++++++++++++++++++++++++-- > > include/uapi/linux/usbdevice_fs.h | 2 + > > 2 files changed, 112 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c > > index fa783531..67dc326 100644 > > --- a/drivers/usb/core/devio.c > > +++ b/drivers/usb/core/devio.c > > @@ -68,6 +68,9 @@ struct usb_dev_state { > > u32 disabled_bulk_eps; > > bool privileges_dropped; > > unsigned long interface_allowed_mask; > > + bool runtime_active; > > + bool is_suspended; > > + wait_queue_head_t wait_resume; > That's some crazy alignment issues, please don't waste bytes for no good > reason. > > And can you document these fields somewhere? > > > > > > }; > > > > struct usb_memory { > > @@ -444,6 +447,23 @@ static struct async *async_getpending(struct > > usb_dev_state *ps, > > return NULL; > > } > > > > +static int async_getpending_count(struct usb_dev_state *ps) > > +{ > > + struct async *as; > > + int count; > > + unsigned long flags; > > + > > + spin_lock_irqsave(&ps->lock, flags); > > + if (list_empty(&ps->async_pending)) > > + count = 0; > > + else > > + list_for_each_entry(as, &ps->async_pending, asynclist) > > + count++; > Doesn't list_for_each_entry() work just fine on an empty list? Just set > count to 0 up above, right? > > > > > + spin_unlock_irqrestore(&ps->lock, flags); > So, right after you call this function, and drop the lock, the entries > can change, making your "count" invalid and stale. So you can not trust > the value at all, right? > > > > > + > > + return count; > > +} > > + > > static void snoop_urb(struct usb_device *udev, > > void __user *userurb, int pipe, unsigned length, > > int timeout_or_status, enum snoop_when when, > > @@ -699,16 +719,26 @@ static void driver_disconnect(struct usb_interface > > *intf) > > destroy_async_on_interface(ps, ifnum); > > } > > > > -/* The following routines are merely placeholders. There is no way > > - * to inform a user task about suspend or resumes. > > - */ > > static int driver_suspend(struct usb_interface *intf, pm_message_t msg) > > { > > + struct usb_dev_state *ps = usb_get_intfdata(intf); > > + > > + ps->is_suspended = true; > No locking needed? > > > > > + snoop(&ps->dev->dev, "driver-suspend\n"); > Why? Does anyone use the snoop api anymore? > > > > > + > > return 0; > > } > > > > static int driver_resume(struct usb_interface *intf) > > { > > + struct usb_dev_state *ps = usb_get_intfdata(intf); > > + > > + ps->runtime_active = true; > > + wake_up(&ps->wait_resume); > > + > > + snoop(&ps->dev->dev, "driver-resume: runtime-active = %d\n", > > + ps->runtime_active); > What does runtime_active give userspace here? Again, who is using > snoop? And isn't runtime_active a bool? It's always going to be "true" > here. Is this just debugging code left in? > > > > > + > > return 0; > > } > > > > @@ -718,6 +748,7 @@ struct usb_driver usbfs_driver = { > > .disconnect = driver_disconnect, > > .suspend = driver_suspend, > > .resume = driver_resume, > > + .supports_autosuspend = 1, > > }; > > > > static int claimintf(struct usb_dev_state *ps, unsigned int ifnum) > > @@ -963,6 +994,27 @@ static struct usb_device *usbdev_lookup_by_devt(dev_t > > devt) > > return to_usb_device(dev); > > } > > > > +/* must be called with usb-dev lock held */ > > +static int usbdev_do_resume(struct usb_dev_state *ps) > > +{ > > + int ret = 0; > > + > > + if (!ps->runtime_active) { > > + snoop(&ps->dev->dev, "suspended..resume now\n"); > Again snoop? > > > > > + ps->is_suspended = false; > > + if (usb_autoresume_device(ps->dev)) { > > + ret = -EIO; > > + goto _out; > > + } > > + snoop(&ps->dev->dev, "resume done..active now\n"); > > + ps->runtime_active = true; > > + wake_up(&ps->wait_resume); > No locking at all? > > > > > + } > > + > > +_out: > Why is this even needed, just return -EIO above and all is good. > > But again, is any locking needed here? > > > > > > + return ret; > > +} > > + > > /* > > * file operations > > */ > > @@ -1008,6 +1060,9 @@ static int usbdev_open(struct inode *inode, struct > > file *file) > > INIT_LIST_HEAD(&ps->async_completed); > > INIT_LIST_HEAD(&ps->memory_list); > > init_waitqueue_head(&ps->wait); > > + init_waitqueue_head(&ps->wait_resume); > > + ps->runtime_active = true; > > + ps->is_suspended = false; > > ps->disc_pid = get_pid(task_pid(current)); > > ps->cred = get_current_cred(); > > smp_wmb(); > > @@ -1034,6 +1089,10 @@ static int usbdev_release(struct inode *inode, struct > > file *file) > > struct async *as; > > > > usb_lock_device(dev); > > + > > + /* what can we can do if resume fails? */ > You tell me! > > > > > + usbdev_do_resume(ps); > > + > > usb_hub_release_all_ports(dev, ps); > > > > list_del_init(&ps->list); > > @@ -2355,6 +2414,18 @@ static int proc_drop_privileges(struct usb_dev_state > > *ps, void __user *arg) > > return 0; > > } > > > > +static int proc_wait_resume(struct usb_dev_state *ps) > > +{ > > + int ret; > > + > > + snoop(&ps->dev->dev, "wait-for-resume\n"); > > + ret = wait_event_interruptible(ps->wait_resume, > > + (ps->runtime_active == true)); > > + snoop(&ps->dev->dev, "wait-for-resume...done\n"); > This is just debugging code, right? Please remove. > > > > > + > > + return ret; > > +} > > + > > /* > > * NOTE: All requests here that have interface numbers as parameters > > * are assuming that somehow the configuration has been prevented from > > @@ -2373,6 +2444,25 @@ static long usbdev_do_ioctl(struct file *file, > > unsigned int cmd, > > > > usb_lock_device(dev); > > > > + if (cmd != USBDEVFS_WAIT_RESUME) { > > + ret = usbdev_do_resume(ps); > do resume for all ioctl commands? are you sure? > > > > > + if (ret) > > + goto done; > > + } else { > > + usb_unlock_device(dev); > > + ret = proc_wait_resume(ps); > > + > > + /* Call auto-resume to balance auto-suspend of suspend- > > ioctl */ > > + usb_lock_device(dev); > > + if (ps->is_suspended) { > > + ret = usb_autoresume_device(ps->dev); > > + ps->is_suspended = false; > > + } > > + usb_unlock_device(dev); > > + > > + goto _done; > What is the difference between _done and done? Please have descriptive > labels if you are going to have any at all. > > Why isn't this part of the switch statement below? > > > > > + } > > + > > /* Reap operations are allowed even after disconnection */ > > switch (cmd) { > > case USBDEVFS_REAPURB: > > @@ -2549,10 +2639,26 @@ static long usbdev_do_ioctl(struct file *file, > > unsigned int cmd, > > case USBDEVFS_GET_SPEED: > > ret = ps->dev->speed; > > break; > > + case USBDEVFS_SUSPEND: > > + ret = 0; > > + > > + /* we cannot suspend when URB is pending */ > > + if (async_getpending_count(ps)) { > > + snoop(&ps->dev->dev, "ioctl-suspend but URB > > pending\n"); > You do not know this, your value is stale :( > > And again, you are using snoop() calls for debugging, not for actual USB > traffic, which is what it was designed for. These all need to be > removed/rewritten. > > > > > + ret = -EINVAL; > > + } else { > > + if (ps->runtime_active) { > > + snoop(&ps->dev->dev, "ioctl-suspend\n"); > > + ps->runtime_active = false; > > + usb_autosuspend_device(ps->dev); > > + } > > + } > > + break; > > } > > > > - done: > > +done: > > usb_unlock_device(dev); > > +_done: > See, horrid names :( > > > > > if (ret >= 0) > > inode->i_atime = current_time(inode); > > return ret; > > diff --git a/include/uapi/linux/usbdevice_fs.h > > b/include/uapi/linux/usbdevice_fs.h > > index 964e872..ae46beb 100644 > > --- a/include/uapi/linux/usbdevice_fs.h > > +++ b/include/uapi/linux/usbdevice_fs.h > > @@ -197,5 +197,7 @@ struct usbdevfs_streams { > > #define USBDEVFS_FREE_STREAMS _IOR('U', 29, struct usbdevfs_streams) > > #define USBDEVFS_DROP_PRIVILEGES _IOW('U', 30, __u32) > > #define USBDEVFS_GET_SPEED _IO('U', 31) > > +#define USBDEVFS_SUSPEND _IO('U', 32) > > +#define USBDEVFS_WAIT_RESUME _IO('U', 33) > No documentation for what these do? > > thanks, > > greg k-h
