There is a custom (non-USB IF) extension to the USB standard:
http://msdn.microsoft.com/library/windows/hardware/gg463182
The said extension is maintained by Microsoft for Microsoft.
Yet it is fairly common for various devices to use it, and a
popular proprietary operating system expects devices to provide
"OS descriptors", so Linux-based USB gadgets whishing to be able
to talk to a variety of operating systems should be able to provide
the "OS descriptors".
This patch adds optional support for gadgets whishing to expose
the so called "OS String" under index 0xEE of language 0.
The contents of the string is generated based on the qw_sign
array and b_vendor_code.
Interested gadgets need to set the cdev->use_os_string flag,
fill cdev->qw_sign with appropriate values and fill cdev->b_vendor_code
with a value of their choice.
This patch does not however implement responding to any vendor-specific
USB requests.
Signed-off-by: Andrzej Pietrasiewicz <andrze...@samsung.com>
---
drivers/usb/gadget/composite.c | 16 ++++++++++++++++
include/linux/usb/composite.h | 14 ++++++++++++++
2 files changed, 30 insertions(+)
diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index fab9064..0bfdb14 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -960,6 +960,22 @@ static int get_string(struct usb_composite_dev *cdev,
return s->bLength;
}
+ if (cdev->use_os_string && language == 0 && id == OS_STRING_IDX) {
+ /*
+ * bLength|bDescriptorType|qwSignature|bMS_VendorCode|bPad
+ * ---------------------------------------------------------
+ * 1 Byte |1 Byte |14 Bytes |1 Byte |1 Byte
+ * ---------------------------------------------------------
+ */
+ u8 *b = buf;
+ b[0] = 0x12;
+ b[1] = USB_DT_STRING;
+ memcpy(&b[2], cdev->qw_sign, OS_STRING_QW_SIGN_LEN);
+ b[2 + OS_STRING_QW_SIGN_LEN] = cdev->b_vendor_code;
+ b[3 + OS_STRING_QW_SIGN_LEN] = 0;
+ return 0x12;
+ }
+
list_for_each_entry(uc, &cdev->gstrings, list) {
struct usb_gadget_strings **sp;
diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index d3ca3b5..28e3b5d 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -335,11 +335,17 @@ static inline struct usb_composite_driver *to_cdriver(
return container_of(gdrv, struct usb_composite_driver, gadget_driver);
}
+#define OS_STRING_QW_SIGN_LEN 14
+#define OS_STRING_IDX 0xEE
+
/**
* struct usb_composite_device - represents one composite usb gadget
* @gadget: read-only, abstracts the gadget's usb peripheral controller
* @req: used for control responses; buffer is pre-allocated
* @config: the currently active configuration
+ * @use_os_string: false by default, interested gadgets set it
+ * @qw_sign: qwSignature part of the OS string
+ * @b_vendor_code: bMS_VendorCode part of the OS string
*
* One of these devices is allocated and initialized before the
* associated device driver's bind() is called.
@@ -372,6 +378,14 @@ struct usb_composite_dev {
struct usb_configuration *config;
+ /*
+ * OS String is a custom (yet popular) extension to the USB standard.
+ *
+ */
+ unsigned int use_os_string:1;
+ u8 qw_sign[OS_STRING_QW_SIGN_LEN];
+ u8 b_vendor_code;
+
/* private: */
/* internals */
unsigned int suspended:1;
--
1.8.3.2
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