From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Kocialkowski Date: Wed, 08 Apr 2015 22:59:36 +0200 Subject: [U-Boot] [PATCH v3 3/3] usb: Early failure when the first descriptor read fails or is invalid In-Reply-To: <5524BF6E.5090308@wwwdotorg.org> References: <1428153149-3738-1-git-send-email-contact@paulk.fr> <1428153149-3738-3-git-send-email-contact@paulk.fr> <5524B779.5090308@wwwdotorg.org> <5524BF6E.5090308@wwwdotorg.org> Message-ID: <1428526776.2401.7.camel@collins> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Le mardi 07 avril 2015 ? 23:41 -0600, Stephen Warren a ?crit : > On 04/07/2015 11:07 PM, Stephen Warren wrote: > > On 04/04/2015 07:12 AM, Paul Kocialkowski wrote: > >> This may happen when using an USB1 device on a controller that only supports > >> USB2 (e.g. EHCI). Reading the first descriptor will fail (read 0 byte), so we > >> can abort the process at this point instead of failing later and wasting time. > > > > FYI, this patch breaks USB keyboard (or perhaps any USB 1.x device) > > support on the RPi. Damn, I'm really sorry about that, I wish I had had more hardware available to test it thoroughly and that I had thought twice about it and foresaw that issue. My sincerest apologies for that mistake and of course, thanks for noticing and picking it up! > >> diff --git a/common/usb.c b/common/usb.c > > > >> @@ -956,7 +956,7 @@ int usb_new_device(struct usb_device *dev) > >> */ > >> #ifndef CONFIG_USB_XHCI > >> err = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, 64); > >> - if (err < 0) { > >> + if (err < sizeof(struct usb_device_descriptor)) { > >> debug("usb_new_device: usb_get_descriptor() failed\n"); > >> return -EIO; > >> } > > > > The value returned here is 8 not 18 (the sizeof the descriptor), so the > > code bails out with an error. That makes sense on USB low speed devices. > > Given the description of what this patch is attempting to achieve, > > shouldn't the replacement check be: > > > > if (err <= 0) { > > > > My guess for why the value 8 is returned is because the device's > > maxpacket is 8, and the DWC2 driver only attempts to transfer 1 packet > > because the requested transfer size is 64, and the default packet size > > is 64, which means 1 packet. Note that DWC2 HW (perhaps unlike e.g. > > EHCI) requires the driver to specify the number of packets transferred, > > not a byte count. However, I haven't validated that yet. My device is a > > USB 1.x FS keyboard. > > Yes, I can avoid the error by hacking dwc2.c's assignment of max: > > > int chunk_msg(struct usb_device *dev, unsigned long pipe, int *pid, int in, > > void *buffer, int len, bool ignore_ack) > > { > ... > > int max = usb_maxpacket(dev, pipe); > > and forcing that to 8 rather than 64 for the data transfer phase of the > first transaction to each USB device (my keyboard has a built-in hub, so > I need to override a few different transactions). > > Thinking about the fix more, perhaps something like the following is > appropriate: > > if (err < offsetof(struct usb_device_descriptor, idVendor)) I would be happy with using 8 directly since that's AFAIK the smallest packet size that should be used on USB. Using offsetof, while not requiring any hardcoded value, seems a bit unclean to me as it abstracts that fact. > ... since idVendor is the first field that's not used by the code that > processes the results of the initial descriptor read. Hopefully there > are no devices with a control endpoint bMaxPacketSize0 less than 8 > (which is what that offsetof evaluates to). > http://www.usbmadesimple.co.uk/ums_3.htm seems to imply that's the case, > saying for control transfers: That makes sense, too. > The max packet size for the data stage is 8 bytes at low speed, 8, 16, > 32 or 64 at full Speed and 64 for high speed. > > (although one of my keyboards has a maxPacket of 4 for EP 2, but I > thinkt hat's something different) > > Also note the comment a little before the code this patch affects in > U-Boot's common/usb.c: > > > /* send 64-byte GET-DEVICE-DESCRIPTOR request. Since the descriptor is > > * only 18 bytes long, this will terminate with a short packet. But if > > * the maxpacket size is 8 or 16 the device may be waiting to transmit > > * some more, or keeps on retransmitting the 8 byte header. */ -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: This is a digitally signed message part URL: