[PATCH v2 1/1] usb: Assimilate usb_get_descriptor() to linux

[Philip Oberfichtner]

Before this commit, usb_get_descriptor() failed for some flakey USB
devices. We hereby adopt the more robust linux implementation [1].

For instance, for the "Alcor Micro Corp. Flash Drive" (VID 0x058f, PID
0x6387), the following behavior occurs from time to time:

=> usb start
starting USB...
Bus xhci_pci: Register 10000840 NbrPorts 16
Starting the controller
USB XHCI 1.20
scanning bus xhci_pci for devices... usb_new_device: Cannot read configuration, skipping device 058f:6387

Signed-off-by: Philip Oberfichtner <pro at denx.de>

[1] From a38297e3fb012 (Linux 6.9), see
    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/usb/core/message.c?h=v6.9#n781
---

Notes:
    Changes in V2: Adapt commit message to
    	- state kernel version
    	- state which exact USB device is being fixed
    	- include error log

 common/usb.c | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/common/usb.c b/common/usb.c
index 99e6b857c7..661ec0a9c4 100644
--- a/common/usb.c
+++ b/common/usb.c
@@ -215,8 +215,9 @@ int usb_int_msg(struct usb_device *dev, unsigned long pipe,
  * clear keyboards LEDs). For data transfers, (storage transfers) we don't
  * allow control messages with 0 timeout, by previousely resetting the flag
  * asynch_allowed (usb_disable_asynch(1)).
- * returns the transferred length if OK or -1 if error. The transferred length
- * and the current status are stored in the dev->act_len and dev->status.
+ * returns the transferred length if OK, otherwise a negative error code. The
+ * transferred length and the current status are stored in the dev->act_len and
+ * dev->status.
  */
 int usb_control_msg(struct usb_device *dev, unsigned int pipe,
 			unsigned char request, unsigned char requesttype,
@@ -258,11 +259,14 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe,
 			break;
 		mdelay(1);
 	}
+
+	if (timeout == 0)
+		return -ETIMEDOUT;
+
 	if (dev->status)
 		return -1;
 
 	return dev->act_len;
-
 }
 
 /*-------------------------------------------------------------------
@@ -563,10 +567,29 @@ int usb_clear_halt(struct usb_device *dev, int pipe)
 static int usb_get_descriptor(struct usb_device *dev, unsigned char type,
 			unsigned char index, void *buf, int size)
 {
-	return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
-			       USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
-			       (type << 8) + index, 0, buf, size,
-			       USB_CNTL_TIMEOUT);
+	int i;
+	int result;
+
+	if (size <= 0)		/* No point in asking for no data */
+		return -EINVAL;
+
+	memset(buf, 0, size);	/* Make sure we parse really received data */
+
+	for (i = 0; i < 3; ++i) {
+		/* retry on length 0 or error; some devices are flakey */
+		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+					 USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
+					 (type << 8) + index, 0, buf, size,
+					 USB_CNTL_TIMEOUT);
+		if (result <= 0 && result != -ETIMEDOUT)
+			continue;
+		if (result > 1 && ((u8 *)buf)[1] != type) {
+			result = -ENODATA;
+			continue;
+		}
+		break;
+	}
+	return result;
 }
 
 /**********************************************************************
-- 
2.39.2