Hi Andrew, David, On Mon, 11 February 2013 David Herrmann wrote: > Thanks a lot for the patch. I think it's fine and I would like to see > it applied upstream: > Reviewed-by: David Herrmann <dh.herrmann@xxxxxxxxx> Reviewed-by: Bruno Prémont <bonbons@xxxxxxxxxxxxxxxxx> > Some small things below. They're just my personal opinion so I am also > ok with this being applied right away. Same from me, with the idea of making possible driver-bugs more visible. Thanks, Bruno > On Sun, Feb 10, 2013 at 6:47 PM, Andrew de los Reyes > <andrew-vger@xxxxxxxxxxxxx> wrote: > > Hi Linux-Input and others, > > > > This is the latest version of the patch to allow device drivers to > > communicate with the corresponding device during probe(). I've > > incorporated many of David Herrmann's suggestions into this revision. > > The most notable change is that by using helper functions, we no > > longer need to have a special magic number return value from probe(). > > > > This patch is part of a patch series to support Logitech touch devices > > (e.g., Wireless Touchpad). The rest of the series is not yet ready for > > discussion here, but those curious can see it here: > > https://github.com/adlr/linux/commits/logitech7 > > > > Thanks for your comments, > > -andrew > > > > This patch separates struct hid_device's driver_lock into two. The > > goal is to allow hid device drivers to receive input during their > > probe() or remove() function calls. This is necessary because some > > drivers need to communicate with the device to determine parameters > > needed during probe (e.g., size of a multi-touch surface), and if > > possible, may perfer to communicate with a device on host-initiated > > disconnect (e.g., to put it into a low-power state). > > > > Historically, three functions used driver_lock: > > > > - hid_device_probe: blocks to acquire lock > > - hid_device_remove: blocks to acquire lock > > - hid_input_report: if locked returns -EBUSY, else acquires lock > > > > This patch adds another lock (driver_input_lock) which is used to > > block input from occurring. The lock behavior is now: > > > > - hid_device_probe: blocks to acq. driver_lock, then driver_input_lock > > - hid_device_remove: blocks to acq. driver_lock, then driver_input_lock > > - hid_input_report: if driver_input_lock locked returns -EBUSY, else > > acquires driver_input_lock > > > > This patch also adds two helper functions to be called during probe() > > or remove(): hid_device_io_start() and hid_device_io_stop(). These > > functions lock and unlock, respectively, driver_input_lock; they also > > make a note of whether they did so that hid-core knows if a driver has > > changed the lock state. > > > > This patch results in no behavior change for existing devices and > > drivers. However, during a probe() or remove() function call in a > > driver, that driver may now selectively call hid_device_io_start() to > > let input events come through, then optionally call > > hid_device_io_stop() to stop them. > > > > Change-Id: I737f6fc15911134b51273acf8d3de92fa5cc0f85 > > --- > > drivers/hid/hid-core.c | 24 +++++++++++++++++++++--- > > include/linux/hid.h | 36 +++++++++++++++++++++++++++++++++++- > > 2 files changed, 56 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c > > index 4da66b4..6a04b72 100644 > > --- a/drivers/hid/hid-core.c > > +++ b/drivers/hid/hid-core.c > > @@ -1097,7 +1097,7 @@ int hid_input_report(struct hid_device *hid, int > > type, u8 *data, int size, int i > > if (!hid) > > return -ENODEV; > > > > - if (down_trylock(&hid->driver_lock)) > > + if (down_trylock(&hid->driver_input_lock)) > > return -EBUSY; > > > > if (!hid->driver) { > > @@ -1150,7 +1150,7 @@ nomem: > > hid_report_raw_event(hid, type, data, size, interrupt); > > > > unlock: > > - up(&hid->driver_lock); > > + up(&hid->driver_input_lock); > > return ret; > > } > > EXPORT_SYMBOL_GPL(hid_input_report); > > @@ -1703,6 +1703,11 @@ static int hid_device_probe(struct device *dev) > > > > if (down_interruptible(&hdev->driver_lock)) > > return -EINTR; > > + if (down_interruptible(&hdev->driver_input_lock)) { > > + ret = -EINTR; > > + goto unlock_driver_lock; > > + } > > + hdev->io_started = false; > > > > if (!hdev->driver) { > > id = hid_match_device(hdev, hdrv); > > @@ -1726,6 +1731,9 @@ static int hid_device_probe(struct device *dev) > > hdev->driver = NULL; > > } > > unlock: > > + if (!hdev->io_started) > > + hid_device_io_start(hdev); > > For symmetry you might use up() here and use the wrapper-functions > only in drivers? I don't know. Jiri should say what he prefers. Then same for the _remove() case, see below > > +unlock_driver_lock: > > up(&hdev->driver_lock); > > return ret; > > } > > @@ -1734,9 +1742,15 @@ static int hid_device_remove(struct device *dev) > > { > > struct hid_device *hdev = container_of(dev, struct hid_device, dev); > > struct hid_driver *hdrv; > > + int ret = 0; > > > > if (down_interruptible(&hdev->driver_lock)) > > return -EINTR; > > + if (down_interruptible(&hdev->driver_input_lock)) { > > + ret = -EINTR; > > + goto unlock_driver_lock; > > + } > > + hdev->io_started = false; > > If we lock driver_input_lock during remove, we might lose important > packages here because the input handler drops them. > > Drivers that require this should deal with it properly, but you might > get annoying timeouts during remove if you do I/O and lose an > important packet here. > > But I think the proper way to fix this is to move I/O handling into > workqueues instead of interrupt-context so we can actually sleep in > handle_input. So I think this is fine. Though the driver would suffer the same timeout if it does not shortcut them when the device is being physically unplugged. So in both cases the driver does need to take explicit action in ->remove() probably even before reenabling I/O in order to "cancel" pending activity prior to doing the removal reconfiguration on logical unplug. > > hdrv = hdev->driver; > > if (hdrv) { > > @@ -1747,8 +1761,11 @@ static int hid_device_remove(struct device *dev) > > hdev->driver = NULL; > > } > > > > + if (!hdev->io_started) > > + hid_device_io_start(hdev); If withing probe we switch to up() we should go for down() here > > +unlock_driver_lock: > > up(&hdev->driver_lock); > > - return 0; > > + return ret; > > } > > > > static int hid_uevent(struct device *dev, struct kobj_uevent_env *env) > > @@ -2126,6 +2143,7 @@ struct hid_device *hid_allocate_device(void) > > init_waitqueue_head(&hdev->debug_wait); > > INIT_LIST_HEAD(&hdev->debug_list); > > sema_init(&hdev->driver_lock, 1); > > + sema_init(&hdev->driver_input_lock, 1); > > > > return hdev; > > err: > > diff --git a/include/linux/hid.h b/include/linux/hid.h > > index 3a95da6..ae7d32d 100644 > > --- a/include/linux/hid.h > > +++ b/include/linux/hid.h > > @@ -481,7 +481,8 @@ struct hid_device { /* device report descriptor */ > > unsigned country; /* HID country */ > > struct hid_report_enum report_enum[HID_REPORT_TYPES]; > > > > - struct semaphore driver_lock; /* protects the current driver */ > > + struct semaphore driver_lock; /* protects the current driver, > > except during input */ > > + struct semaphore driver_input_lock; /* protects the current driver */ > > struct device dev; /* device */ > > struct hid_driver *driver; > > struct hid_ll_driver *ll_driver; > > @@ -502,6 +503,7 @@ struct hid_device { /* device report descriptor */ > > unsigned int status; /* see STAT flags above */ > > unsigned claimed; /* Claimed by hidinput, hiddev? */ > > unsigned quirks; /* Various quirks the device can pull on us */ > > + bool io_started; /* Protected by driver_lock. If IO has started */ > > > > struct list_head inputs; /* The list of inputs */ > > void *hiddev; /* The hiddev structure */ > > @@ -622,6 +624,10 @@ struct hid_usage_id { > > * @resume: invoked on resume if device was not reset (NULL means nop) > > * @reset_resume: invoked on resume if device was reset (NULL means nop) > > * > > + * probe should return -errno on error, or 0 on success. During probe, > > + * input will not be passed to raw_event unless hid_device_io_start is > > + * called. > > + * > > * raw_event and event should return 0 on no action performed, 1 when no > > * further processing should be done and negative on error > > * > > @@ -742,6 +748,34 @@ const struct hid_device_id *hid_match_id(struct > > hid_device *hdev, > > const struct hid_device_id *id); > > > > /** > > + * hid_device_io_start - enable HID input during probe, remove > > + * > > + * @hid - the device > > + * > > + * This should only be called during probe or remove. It will allow > > + * incoming packets to be delivered to the driver. > > + */ > > +static inline void hid_device_io_start(struct hid_device *hid) { > > + up(&hid->driver_input_lock); > > + hid->io_started = true; > > Shouldn't these lines be swapped? Doesn't matter but it looks weird to > me this way. > > But more importantly, we must go sure this is called from the same > thread that probe() is called on. Other use-cases are not supported by > semaphores and might break due to missing barriers. So maybe the > comment could include that? Maybe even check what value hid->io_started has and WARN() [+skip up()/down()] in case hid_device_io_start()/stop() was not called in a balanced way. > > +} > > + > > +/** > > + * hid_device_io_stop - disable HID input during probe, remove > > + * > > + * @hid - the device > > + * > > + * Should only be called after hid_device_io_start. It will prevent > > + * incoming packets from going to the driver for the duration of > > + * probe, remove. If called during probe, packets will still go to the > > + * driver after probe is complete. > > + */ > > +static inline void hid_device_io_stop(struct hid_device *hid) { > > + hid->io_started = false; > > + down(&hid->driver_input_lock); > > Same. Same as _start() here > > +} > > + > > +/** > > * hid_map_usage - map usage input bits > > * > > * @hidinput: hidinput which we are interested in > > -- > > 1.8.1 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
