6.4-stable review patch. If anyone has any objections, please let me know.
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From: Alan Stern stern@rowland.harvard.edu
commit 85d07c55621676d47d873d2749b88f783cd4d5a1 upstream.
In preparation for reworking the usb_get_device_descriptor() routine, it is desirable to unite the two different code paths responsible for initially determining endpoint 0's maximum packet size in a newly discovered USB device. Making this determination presents a chicken-and-egg sort of problem, in that the only way to learn the maxpacket value is to get it from the device descriptor retrieved from the device, but communicating with the device to retrieve a descriptor requires us to know beforehand the ep0 maxpacket size.
In practice this problem is solved in two different ways, referred to in hub.c as the "old scheme" and the "new scheme". The old scheme (which is the approach recommended by the USB-2 spec) involves asking the device to send just the first eight bytes of its device descriptor. Such a transfer uses packets containing no more than eight bytes each, and every USB device must have an ep0 maxpacket size
= 8, so this should succeed. Since the bMaxPacketSize0 field of the
device descriptor lies within the first eight bytes, this is all we need.
The new scheme is an imitation of the technique used in an early Windows USB implementation, giving it the happy advantage of working with a wide variety of devices (some of them at the time would not work with the old scheme, although that's probably less true now). It involves making an initial guess of the ep0 maxpacket size, asking the device to send up to 64 bytes worth of its device descriptor (which is only 18 bytes long), and then resetting the device to clear any error condition that might have resulted from the guess being wrong. The initial guess is determined by the connection speed; it should be correct in all cases other than full speed, for which the allowed values are 8, 16, 32, and 64 (in this case the initial guess is 64).
The reason for this patch is that the old- and new-scheme parts of hub_port_init() use different code paths, one involving usb_get_device_descriptor() and one not, for their initial reads of the device descriptor. Since these reads have essentially the same purpose and are made under essentially the same circumstances, this is illogical. It makes more sense to have both of them use a common subroutine.
This subroutine does basically what the new scheme's code did, because that approach is more general than the one used by the old scheme. It only needs to know how many bytes to transfer and whether or not it is being called for the first iteration of a retry loop (in case of certain time-out errors). There are two main differences from the former code:
We initialize the bDescriptorType field of the transfer buffer to 0 before performing the transfer, to avoid possibly accessing an uninitialized value afterward.
We read the device descriptor into a temporary buffer rather than storing it directly into udev->descriptor, which the old scheme implementation used to do.
Since the whole point of this first read of the device descriptor is to determine the bMaxPacketSize0 value, that is what the new routine returns (or an error code). The value is stored in a local variable rather than in udev->descriptor. As a side effect, this necessitates moving a section of code that checks the bcdUSB field for SuperSpeed devices until after the full device descriptor has been retrieved.
Signed-off-by: Alan Stern stern@rowland.harvard.edu Cc: Oliver Neukum oneukum@suse.com Link: https://lore.kernel.org/r/495cb5d4-f956-4f4a-a875-1e67e9489510@rowland.harva... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/core/hub.c | 173 ++++++++++++++++++++++++++----------------------- 1 file changed, 94 insertions(+), 79 deletions(-)
--- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -4703,6 +4703,67 @@ static int hub_enable_device(struct usb_ return hcd->driver->enable_device(hcd, udev); }
+/* + * Get the bMaxPacketSize0 value during initialization by reading the + * device's device descriptor. Since we don't already know this value, + * the transfer is unsafe and it ignores I/O errors, only testing for + * reasonable received values. + * + * For "old scheme" initialization, size will be 8 so we read just the + * start of the device descriptor, which should work okay regardless of + * the actual bMaxPacketSize0 value. For "new scheme" initialization, + * size will be 64 (and buf will point to a sufficiently large buffer), + * which might not be kosher according to the USB spec but it's what + * Windows does and what many devices expect. + * + * Returns: bMaxPacketSize0 or a negative error code. + */ +static int get_bMaxPacketSize0(struct usb_device *udev, + struct usb_device_descriptor *buf, int size, bool first_time) +{ + int i, rc; + + /* + * Retry on all errors; some devices are flakey. + * 255 is for WUSB devices, we actually need to use + * 512 (WUSB1.0[4.8.1]). + */ + for (i = 0; i < GET_MAXPACKET0_TRIES; ++i) { + /* Start with invalid values in case the transfer fails */ + buf->bDescriptorType = buf->bMaxPacketSize0 = 0; + rc = usb_control_msg(udev, usb_rcvaddr0pipe(), + USB_REQ_GET_DESCRIPTOR, USB_DIR_IN, + USB_DT_DEVICE << 8, 0, + buf, size, + initial_descriptor_timeout); + switch (buf->bMaxPacketSize0) { + case 8: case 16: case 32: case 64: case 255: + if (buf->bDescriptorType == USB_DT_DEVICE) { + rc = buf->bMaxPacketSize0; + break; + } + fallthrough; + default: + if (rc >= 0) + rc = -EPROTO; + break; + } + + /* + * Some devices time out if they are powered on + * when already connected. They need a second + * reset, so return early. But only on the first + * attempt, lest we get into a time-out/reset loop. + */ + if (rc > 0 || (rc == -ETIMEDOUT && first_time && + udev->speed > USB_SPEED_FULL)) + break; + } + return rc; +} + +#define GET_DESCRIPTOR_BUFSIZE 64 + /* Reset device, (re)assign address, get device descriptor. * Device connection must be stable, no more debouncing needed. * Returns device in USB_STATE_ADDRESS, except on error. @@ -4727,6 +4788,12 @@ hub_port_init(struct usb_hub *hub, struc int devnum = udev->devnum; const char *driver_name; bool do_new_scheme; + int maxp0; + struct usb_device_descriptor *buf; + + buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO); + if (!buf) + return -ENOMEM;
/* root hub ports have a slightly longer reset period * (from USB 2.0 spec, section 7.1.7.5) @@ -4846,9 +4913,6 @@ hub_port_init(struct usb_hub *hub, struc }
if (do_new_scheme) { - struct usb_device_descriptor *buf; - int r = 0; - retval = hub_enable_device(udev); if (retval < 0) { dev_err(&udev->dev, @@ -4857,52 +4921,8 @@ hub_port_init(struct usb_hub *hub, struc goto fail; }
-#define GET_DESCRIPTOR_BUFSIZE 64 - buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO); - if (!buf) { - retval = -ENOMEM; - continue; - } - - /* Retry on all errors; some devices are flakey. - * 255 is for WUSB devices, we actually need to use - * 512 (WUSB1.0[4.8.1]). - */ - for (operations = 0; operations < GET_MAXPACKET0_TRIES; - ++operations) { - buf->bMaxPacketSize0 = 0; - r = usb_control_msg(udev, usb_rcvaddr0pipe(), - USB_REQ_GET_DESCRIPTOR, USB_DIR_IN, - USB_DT_DEVICE << 8, 0, - buf, GET_DESCRIPTOR_BUFSIZE, - initial_descriptor_timeout); - switch (buf->bMaxPacketSize0) { - case 8: case 16: case 32: case 64: case 255: - if (buf->bDescriptorType == - USB_DT_DEVICE) { - r = 0; - break; - } - fallthrough; - default: - if (r == 0) - r = -EPROTO; - break; - } - /* - * Some devices time out if they are powered on - * when already connected. They need a second - * reset. But only on the first attempt, - * lest we get into a time out/reset loop - */ - if (r == 0 || (r == -ETIMEDOUT && - retries == 0 && - udev->speed > USB_SPEED_FULL)) - break; - } - udev->descriptor.bMaxPacketSize0 = - buf->bMaxPacketSize0; - kfree(buf); + maxp0 = get_bMaxPacketSize0(udev, buf, + GET_DESCRIPTOR_BUFSIZE, retries == 0);
retval = hub_port_reset(hub, port1, udev, delay, false); if (retval < 0) /* error or disconnect */ @@ -4913,14 +4933,13 @@ hub_port_init(struct usb_hub *hub, struc retval = -ENODEV; goto fail; } - if (r) { - if (r != -ENODEV) + if (maxp0 < 0) { + if (maxp0 != -ENODEV) dev_err(&udev->dev, "device descriptor read/64, error %d\n", - r); - retval = -EMSGSIZE; + maxp0); + retval = maxp0; continue; } -#undef GET_DESCRIPTOR_BUFSIZE }
/* @@ -4966,19 +4985,17 @@ hub_port_init(struct usb_hub *hub, struc break; }
- retval = usb_get_device_descriptor(udev, 8); - if (retval < 8) { + /* !do_new_scheme || wusb */ + maxp0 = get_bMaxPacketSize0(udev, buf, 8, retries == 0); + if (maxp0 < 0) { + retval = maxp0; if (retval != -ENODEV) dev_err(&udev->dev, "device descriptor read/8, error %d\n", retval); - if (retval >= 0) - retval = -EMSGSIZE; } else { u32 delay;
- retval = 0; - delay = udev->parent->hub_delay; udev->hub_delay = min_t(u32, delay, USB_TP_TRANSMISSION_DELAY_MAX); @@ -4995,27 +5012,10 @@ hub_port_init(struct usb_hub *hub, struc if (retval) goto fail;
- /* - * Some superspeed devices have finished the link training process - * and attached to a superspeed hub port, but the device descriptor - * got from those devices show they aren't superspeed devices. Warm - * reset the port attached by the devices can fix them. - */ - if ((udev->speed >= USB_SPEED_SUPER) && - (le16_to_cpu(udev->descriptor.bcdUSB) < 0x0300)) { - dev_err(&udev->dev, "got a wrong device descriptor, " - "warm reset device\n"); - hub_port_reset(hub, port1, udev, - HUB_BH_RESET_TIME, true); - retval = -EINVAL; - goto fail; - } - - if (udev->descriptor.bMaxPacketSize0 == 0xff || - udev->speed >= USB_SPEED_SUPER) + if (maxp0 == 0xff || udev->speed >= USB_SPEED_SUPER) i = 512; else - i = udev->descriptor.bMaxPacketSize0; + i = maxp0; if (usb_endpoint_maxp(&udev->ep0.desc) != i) { if (udev->speed == USB_SPEED_LOW || !(i == 8 || i == 16 || i == 32 || i == 64)) { @@ -5041,6 +5041,20 @@ hub_port_init(struct usb_hub *hub, struc goto fail; }
+ /* + * Some superspeed devices have finished the link training process + * and attached to a superspeed hub port, but the device descriptor + * got from those devices show they aren't superspeed devices. Warm + * reset the port attached by the devices can fix them. + */ + if ((udev->speed >= USB_SPEED_SUPER) && + (le16_to_cpu(udev->descriptor.bcdUSB) < 0x0300)) { + dev_err(&udev->dev, "got a wrong device descriptor, warm reset device\n"); + hub_port_reset(hub, port1, udev, HUB_BH_RESET_TIME, true); + retval = -EINVAL; + goto fail; + } + usb_detect_quirks(udev);
if (udev->wusb == 0 && le16_to_cpu(udev->descriptor.bcdUSB) >= 0x0201) { @@ -5063,6 +5077,7 @@ fail: hub_port_disable(hub, port1, 0); update_devnum(udev, devnum); /* for disconnect processing */ } + kfree(buf); return retval; }