linux-kernel - [PATCH v2] HID: leave dev_rdesc unmodified and use it for comparisons

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Date:	Tue, 18 Sep 2012 19:36:33 -0700
From:	Kevin Daughtridge <kevin@...u.com>
To:	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org
CC:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Henrik Rydberg <rydberg@...omail.se>,
	Kevin Daughtridge <kevin@...u.com>
Subject: [PATCH v2] HID: leave dev_rdesc unmodified and use it for comparisons

The dev_rdesc member of the hid_device structure is meant to store the original
report descriptor received from the device, but it is currently passed to any
report_fixup method before it is copied to the rdesc member. This patch moves
the kmemdup to before, not after, the report_fixup call, keeping dev_rdesc
unchanged.

usbhid's hid_post_reset checks the report descriptor currently returned by the
device against a descriptor that may have been modified by a driver's
report_fixup method. That leaves some devices nonfunctional after a resume, with
a "reset_resume error 1" reported. This patch checks the new descriptor against
the unmodified dev_rdesc instead.

BugLink:http://bugs.launchpad.net/bugs/1049623
Signed-off-by: Kevin Daughtridge<kevin@...u.com>
---
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -775,12 +775,14 @@ int hid_open_report(struct hid_device *d
  		return -ENODEV;
  	size = device->dev_rsize;
  
+	start = kmemdup(start, size, GFP_KERNEL);
+	if (start == NULL)
+		return -ENOMEM;
+
  	if (device->driver->report_fixup)
  		start = device->driver->report_fixup(device, start, &size);
  
-	device->rdesc = kmemdup(start, size, GFP_KERNEL);
-	if (device->rdesc == NULL)
-		return -ENOMEM;
+	device->rdesc = start;
  	device->rsize = size;
  
  	parser = vzalloc(sizeof(struct hid_parser));
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -1436,7 +1436,7 @@ static int hid_post_reset(struct usb_int
  		kfree(rdesc);
  		return 1;
  	}
-	status = memcmp(rdesc, hid->rdesc, hid->rsize);
+	status = memcmp(rdesc, hid->dev_rdesc, hid->rsize);
  	kfree(rdesc);
  	if (status != 0) {
  		dbg_hid("report descriptor changed\n");

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