Re: [PATCH] usb: gadget: f_hid: added GET_IDLE and SET_IDLE handlers

[Maxim Devaev <mdevaev@gmail.com>]

> Felipe Balbi <balbi@kernel.org> writes:
> 
> yeah, I don't see any issues with this. If you have access to the tool,
> mind running USBCV on the f_hid gadget? Would be cool to get some
> confirmation that we're within spec.

Thanks for pointing to USBCV. I used a hardware USB protocol analyzer
to understand what was wrong with f_hid, and my hosts only sent idle=0.
Thanks to the test, I realized that I should only use the upper byte
that contains duration. Here a fixed version of the patch,
which successfully passes all HID tests. The idle part:

    Now Starting Test: HID Class GET/SET Idle Test (Configuration Index 0)
    Start time: Jul 22, 2021 - 20:29:40
    No report IDs found in report descriptor for Interface : 0x0
    GET/SETIdle test for report ID 0. Setting Idle rate to : 0x7F
    No report IDs found in report descriptor for Interface : 0x1
    GET/SETIdle test for report ID 0. Setting Idle rate to : 0x7F
    
    Stop time: Jul 22, 2021 - 20:29:41
    Duration:  1 second.
    Stopping Test [ HID Class GET/SET Idle Test (Configuration Index 0):
         Number of: Fails (0); Aborts (0); Warnings (0) ]


From ac56ddc1ab2dfa599a12a3bf064e520d587e89fe Mon Sep 17 00:00:00 2001
From: Maxim Devaev <mdevaev@gmail.com>
Date: Wed, 21 Jul 2021 20:48:28 +0300
Subject: [PATCH] usb: gadget: f_hid: added GET_IDLE and SET_IDLE handlers

The USB HID standard declares mandatory support for GET_IDLE and SET_IDLE
requests for Boot Keyboard. Most hosts can handle their absence, but others
like some old/strange UEFIs and BIOSes consider this a critical error
and refuse to work with f_hid.

This primitive implementation of saving and returning idle is sufficient
to meet the requirements of the standard and these devices.

Signed-off-by: Maxim Devaev <mdevaev@gmail.com>
---
 drivers/usb/gadget/function/f_hid.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index 02683ac07..1010f0a3e 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -41,6 +41,7 @@ struct f_hidg {
 	unsigned char			bInterfaceSubClass;
 	unsigned char			bInterfaceProtocol;
 	unsigned char			protocol;
+	unsigned char			idle;
 	unsigned short			report_desc_length;
 	char				*report_desc;
 	unsigned short			report_length;
@@ -523,6 +524,14 @@ static int hidg_setup(struct usb_function *f,
 		goto respond;
 		break;
 
+	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
+		  | HID_REQ_GET_IDLE):
+		VDBG(cdev, "get_idle\n");
+		length = min_t(unsigned int, length, 1);
+		((u8 *) req->buf)[0] = hidg->idle;
+		goto respond;
+		break;
+
 	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
 		  | HID_REQ_SET_REPORT):
 		VDBG(cdev, "set_report | wLength=%d\n", ctrl->wLength);
@@ -546,6 +555,14 @@ static int hidg_setup(struct usb_function *f,
 		goto stall;
 		break;
 
+	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
+		  | HID_REQ_SET_IDLE):
+		VDBG(cdev, "set_idle\n");
+		length = 0;
+		hidg->idle = value >> 8;
+		goto respond;
+		break;
+
 	case ((USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_INTERFACE) << 8
 		  | USB_REQ_GET_DESCRIPTOR):
 		switch (value >> 8) {
@@ -773,6 +790,7 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
 	hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
 	hidg->protocol = HID_REPORT_PROTOCOL;
+	hidg->idle = 1;
 	hidg_ss_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
 	hidg_ss_in_comp_desc.wBytesPerInterval =
 				cpu_to_le16(hidg->report_length);
-- 
2.32.0