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author | Stephen Warren <swarren@wwwdotorg.org> | 2015-04-09 03:27:49 (GMT) |
---|---|---|
committer | Marek Vasut <marex@denx.de> | 2015-04-14 03:47:48 (GMT) |
commit | 25c0673635da1bef75ab5a9d852f92e0f0b581df (patch) | |
tree | a9775543b080f9f2046beda702aa02c8dffe97a5 | |
parent | 04ee6ee2ca5ad419ebcbc64dae6e7128f32156fd (diff) | |
download | u-boot-25c0673635da1bef75ab5a9d852f92e0f0b581df.tar.xz |
usb: fix first descriptor fetch error handling
When fetching the first descriptor from a new device, only validate that
we received at least 8 bytes, not that we received the entire descriptor.
The reasoning is:
- The code only uses fields in the first 8 bytes, so that's all we need
to have fetched at this stage.
- The smallest maxpacket size is 8 bytes. Before we know the actual
maxpacket the device uses, the USB controller may only accept a single
packet (see the DWC2 note in the comment added in the commit).
Consequently we are only guaranteed to receive 1 packet (at least 8
bytes) even in a non-error case.
Fixes: 1a7758044b04 ("usb: Early failure when the first descriptor read
fails or is invalid")
Cc: Paul Kocialkowski <contact@paulk.fr>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
-rw-r--r-- | common/usb.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/common/usb.c b/common/usb.c index f648847..bf76c41 100644 --- a/common/usb.c +++ b/common/usb.c @@ -956,7 +956,22 @@ 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 < sizeof(struct usb_device_descriptor)) { + /* + * Validate we've received only at least 8 bytes, not that we've + * received the entire descriptor. The reasoning is: + * - The code only uses fields in the first 8 bytes, so that's all we + * need to have fetched at this stage. + * - The smallest maxpacket size is 8 bytes. Before we know the actual + * maxpacket the device uses, the USB controller may only accept a + * single packet. Consequently we are only guaranteed to receive 1 + * packet (at least 8 bytes) even in a non-error case. + * + * At least the DWC2 controller needs to be programmed with the number + * of packets in addition to the number of bytes. A request for 64 + * bytes of data with the maxpacket guessed as 64 (above) yields a + * request for 1 packet. + */ + if (err < 8) { debug("usb_new_device: usb_get_descriptor() failed\n"); return -EIO; } |