Hi! On Wed, May 11, 2022 at 10:09:26AM -0400, Alan Stern wrote: >On Wed, May 11, 2022 at 01:13:17AM +0200, Michael Grzeschik wrote: >> This patch adds an sysfs switch to enable/disable a port on an power >> switchable hub. It also ensures that the associated device gets >> disconnected from the logical usb tree. > >This says what the patch does. It does not explain why the patch was >written or why anybody would want to switch the power on a hub's port. Good point. This goes together with the missing ABI documentation. I will fix it in the v2. >> Signed-off-by: Michael Grzeschik >> --- >> drivers/usb/core/port.c | 47 +++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 47 insertions(+) >> >> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c >> index d5bc36ca5b1f77..abc618d87888f3 100644 >> --- a/drivers/usb/core/port.c >> +++ b/drivers/usb/core/port.c >> @@ -17,6 +17,52 @@ static int usb_port_block_power_off; >> >> static const struct attribute_group *port_dev_group[]; >> >> +static ssize_t port_power_store(struct device *dev, struct device_attribute *attr, >> + const char *buf, size_t count) >> +{ >> + struct usb_port *port_dev = to_usb_port(dev); >> + struct usb_device *udev = port_dev->child; >> + struct usb_device *hdev = to_usb_device(dev->parent->parent); >> + struct usb_hub *hub = usb_hub_to_struct_hub(hdev); >> + int port1 = port_dev->portnum; >> + bool value; >> + int rc = 0; >> + >> + if (!hub) >> + return -EINVAL; >> + >> + if (hub->in_reset) >> + return -EBUSY; > >What point is there in doing this test? The value of hub->in_reset may >change an instant later. Unless you acquire the hub's lock first. >For that matter, you should be holding the hub's lock while you call >usb_hub_to_struct_hub() -- unless you don't care if the hub gets >disconnected while this routine is running. Or if udev does. I could remove it for the sake of simplicity in the first version. If this will matter in the future we can add it then. >> + >> + rc = strtobool(buf, &value); >> + if (rc) >> + return rc; >> + >> + if (value) >> + usb_remote_wakeup(hdev); > >Why call usb_remote_wakeup()? The function was not intended to be used >this way; it was meant to be used when a device sends a wakeup request. I found this function was called when plugging in a device into an suspended hub. So it seemed to be the right thing to do. >Furthermore, nothing prevents the hub from going back into runtime >suspend the moment this function completes. OK. That needs to be locked than. Is it with usb_autopm_get_interface and usb_autopm_put_interface? >If you want to bring a USB device out of runtime suspend, call >usb_autoresume_device(). And then don't forget to call >usb_autosuspend_device() when you're done with it. In case the hub had only one device attached to one one port. When I called this sysfs function on that port, the hub would suspend afterwards. Which is probably a correct way to go for a hub with no active devices attached. When replacing usb_remote_wakeup with usb_autoresume_device this works exactly the same. So I will replace it in v2. The extra usb_autosuspend_device for the hub is probably not necessary. >> + >> + rc = usb_hub_set_port_power(hdev, hub, port1, value); >> + if (rc) >> + return rc; > >You probably should acquire the port's lock before doing this. >Otherwise some other thread might be doing something else to the port at >the same time. Yes. I will do that in v2. >> + >> + if (!value) { >> + usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION); >> + if (!port_dev->is_superspeed) >> + usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE); >> + >> + if (udev) { >> + port_dev->child = NULL; > >That assignment is not necessary; usb_disconnect() will take care of it. Here are two things that are in play. First I have to set port_dev->child = NULL before calling usb_disconnect. Otherwise the following automatic hub_suspend call (in case this was the last operational port of the hub) will print the message "device x-y not suspended yet" and will fail the hub to suspend. When calling usb_autoresume_device(udev) instead and before calling usb_disconnect, this is no longer the case. The hub will be succesfully suspended. The second thing is the assignment. I still have to explicitly assign NULL to port_dev->child. Otherwise a following enable of this port via this sysfs will run into an hub_event with the usb_disonnect for the device on that port. But this will spit out a ugly traceback leading with the following error: [ 21.718574] usb 2-1.1: USB disconnect, device number -1 [ 21.719100] Unable to handle kernel paging request at virtual address 96d628cc24e2e078 [ 21.719807] Mem abort info: [ 21.720065] ESR = 0x96000044 [ 21.720348] EC = 0x25: DABT (current EL), IL = 32 bits [ 21.720827] SET = 0, FnV = 0 [ 21.721109] EA = 0, S1PTW = 0 [ 21.721447] FSC = 0x04: level 0 translation fault [ 21.721891] Data abort info: [ 21.722157] ISV = 0, ISS = 0x00000044 [ 21.722505] CM = 0, WnR = 1 [ 21.722779] [96d628cc24e2e078] address between user and kernel address ranges [ 21.723429] Internal error: Oops: 96000044 [#1] PREEMPT SMP [ 21.723927] Modules linked in: uio_pdrv_genirq fuse [ 21.724380] CPU: 0 PID: 58 Comm: kworker/0:3 Not tainted 5.18.0-rc6+ #93 [ 21.724977] Hardware name: Radxa ROCK3 Model A (DT) [ 21.725412] Workqueue: usb_hub_wq hub_event [ 21.725802] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 21.726419] pc : usb_disable_endpoint+0x7c/0xdc [ 21.726832] lr : usb_disable_device_endpoints+0xbc/0xe0 [ 21.727301] sp : ffffffc009b33b30 [ 21.727597] x29: ffffffc009b33b30 x28: ffffff8003ad4ed8 x27: 0000000000000001 [ 21.728239] x26: ffffff8004344928 x25: 0000000000000000 x24: ffffffc0096eb8e0 [ 21.728885] x23: ffffff80043448a8 x22: ffffff8003961800 x21: 0000000000000001 [ 21.729527] x20: 96d628cc24e2e034 x19: ffffff8004344800 x18: ffffffffffffffff [ 21.730168] x17: 0000000000000001 x16: 0000000000000001 x15: ffffffc089b33857 [ 21.730810] x14: 0000000000000000 x13: 312d207265626d75 x12: 6e20656369766564 [ 21.731452] x11: 00000000fffff7ff x10: 00000000fffff7ff x9 : ffffffc00871b8dc [ 21.732093] x8 : 000000000000bfe8 x7 : ffffffc009b33a38 x6 : 0000000000000001 [ 21.732733] x5 : ffffffc009569000 x4 : ffffffc009569050 x3 : ffffff8004344878 [ 21.733374] x2 : 0000000000000001 x1 : 000000000000008f x0 : 0000000000000001 [ 21.734015] Call trace: [ 21.734235] usb_disable_endpoint+0x7c/0xdc [ 21.734616] usb_disable_device_endpoints+0xbc/0xe0 [ 21.735054] usb_disable_device+0x1c0/0x260 [ 21.735432] usb_disconnect+0x108/0x300 [ 21.735778] hub_event+0x1378/0x19c0 [ 21.736102] process_one_work+0x220/0x49c [ 21.736469] worker_thread+0x154/0x450 [ 21.736810] kthread+0xfc/0x110 [ 21.737096] ret_from_fork+0x10/0x20 [ 21.737429] Code: f941c474 340001e0 f901c47f b4ffff14 (b900469f) [ 21.737970] ---[ end trace 0000000000000000 ]--- Did I miss something? >> + usb_disconnect(&udev); >> + } >> + } > >Alan Stern Thanks, Michael Grzeschik -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |