Hi Peter,
W dniu 4.04.2024 o 12:06, Peter Korsgaard pisze:
The OS descriptors logic had the high/low byte of w_value inverted, causing
the extended properties to not be accessible for interface != 0.
Out of curiosity - did you run into problems running some USB gadget,
and if yes, what was it? Or is this patch a result of a code and documentation
review without actually running a gadget?
From the Microsoft documentation:
https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-os-1-0-descriptors-specification
OS_Desc_CompatID.doc (w_index = 0x4):
- wValue:
High Byte = InterfaceNumber. InterfaceNumber is set to the number of the
interface or function that is associated with the descriptor, typically
0x00. Because a device can have only one extended compat ID descriptor,
it should ignore InterfaceNumber, regardless of the value, and simply
return the descriptor.
Low Byte = 0. PageNumber is used to retrieve descriptors that are larger
than 64 KB. The header section is 16 bytes, so PageNumber is set to 0 for
this request.
We currently do not support >64KB compat ID descriptors, so verify that the
low byte is 0.
OS_Desc_Ext_Prop.doc (w_index = 0x5):
- wValue:
High byte = InterfaceNumber. The high byte of wValue is set to the number
of the interface or function that is associated with the descriptor.
Low byte = PageNumber. The low byte of wValue is used to retrieve
descriptors that are larger than 64 KB. The header section is 10 bytes, so
PageNumber is set to 0 for this request.
FWIW w_value is:
u16 w_value = le16_to_cpu(ctrl->wValue);
Regards,
Andrzej
We also don't support >64KB extended properties, so verify that the low byte
is 0 and use the high byte for the interface number.
Fixes: 37a3a533429e ("usb: gadget: OS Feature Descriptors support")
Signed-off-by: Peter Korsgaard <peter@xxxxxxxxxxxxx>
---
drivers/usb/gadget/composite.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 0ace45b66a31..0e151b54aae8 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -2112,7 +2112,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
buf[5] = 0x01;
switch (ctrl->bRequestType & USB_RECIP_MASK) {
case USB_RECIP_DEVICE:
- if (w_index != 0x4 || (w_value >> 8))
+ if (w_index != 0x4 || (w_value & 0xff))
break;
buf[6] = w_index;
/* Number of ext compat interfaces */
@@ -2128,9 +2128,9 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
}
break;
case USB_RECIP_INTERFACE:
- if (w_index != 0x5 || (w_value >> 8))
+ if (w_index != 0x5 || (w_value & 0xff))
break;
- interface = w_value & 0xFF;
+ interface = w_value >> 8;
if (interface >= MAX_CONFIG_INTERFACES ||
!os_desc_cfg->interface[interface])
break;
