linux-kernel - [PATCH 8/9] [HSLPM] usb: gadget: Allow a non-SuperSpeed gadget to support LPM

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Date:   Fri, 28 Apr 2017 12:55:20 +0400
From:   Sevak Arakelyan <SEVAK.ARAKELYAN@...opsys.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     John Youn <John.Youn@...opsys.com>,
        Sevak Arakelyan <SEVAK.ARAKELYAN@...opsys.com>
Subject: [PATCH 8/9] [HSLPM] usb: gadget: Allow a non-SuperSpeed gadget to support LPM

From: John Youn <johnyoun@...opsys.com>

This commit allows a gadget that does not support SuperSpeed to indicate
that it supports LPM. It does this by setting the 'lpm_capable' flag in
the gadget structure.

If a gadget sets this, the composite gadget framework will set the
bcdUSB to 0x0201 to indicate that this supports BOS descriptors, and
also return a USB 2.0 Extension descriptor as part of the BOS descriptor
set.

See USB 2.0 LPM ECN Section 3.

Signed-off-by: John Youn <johnyoun@...opsys.com>
Signed-off-by: Sevak Arakelyan <sevaka@...opsys.com>
---
 drivers/usb/gadget/composite.c | 8 ++++++--
 include/linux/usb/gadget.h     | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index abec93ab81ee..d62f53d7f418 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1608,7 +1608,10 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 					cdev->desc.bcdUSB = cpu_to_le16(0x0210);
 				}
 			} else {
-				cdev->desc.bcdUSB = cpu_to_le16(0x0200);
+				if (gadget->lpm_capable)
+					cdev->desc.bcdUSB = cpu_to_le16(0x0201);
+				else
+					cdev->desc.bcdUSB = cpu_to_le16(0x0200);
 			}
 
 			value = min(w_length, (u16) sizeof cdev->desc);
@@ -1639,7 +1642,8 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 				value = min(w_length, (u16) value);
 			break;
 		case USB_DT_BOS:
-			if (gadget_is_superspeed(gadget)) {
+			if (gadget_is_superspeed(gadget) ||
+			    gadget->lpm_capable) {
 				value = bos_desc(cdev);
 				value = min(w_length, (u16) value);
 			}
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index e4516e9ded0f..927df464100d 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -352,6 +352,8 @@ struct usb_gadget_ops {
  * @deactivated: True if gadget is deactivated - in deactivated state it cannot
  *	be connected.
  * @connected: True if gadget is connected.
+ * @lpm_capable: If the gadget max_speed is FULL or HIGH, this flag
+ *	indicates that it supports LPM as per the LPM ECN & errata.
  *
  * Gadgets have a mostly-portable "gadget driver" implementing device
  * functions, handling all usb configurations and interfaces.  Gadget
@@ -404,6 +406,7 @@ struct usb_gadget {
 	unsigned			is_selfpowered:1;
 	unsigned			deactivated:1;
 	unsigned			connected:1;
+	unsigned			lpm_capable:1;
 };
 #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
 
-- 
2.11.0