[PATCH v2 1/1] HID: logitech: read all 32 bits of report type bitfield

From: Nestor Lopez Casado
Date: Fri May 11 2012 - 10:19:35 EST

From: Jonathan Nieder <jrnieder@xxxxxxxxx>

On big-endian systems (e.g., Apple PowerBook), trying to use a
logitech wireless mouse with the Logitech Unifying Receiver does not
work with v3.2 and later kernels. The device doesn't show up in
/dev/input. Older kernels work fine.

That is because the new hid-logitech-dj driver claims the device. The
device arrival notification appears:

20 00 41 02 00 00 00 00 00 00 00 00 00 00 00

and we read the report_types bitfield (02 00 00 00) to find out what
kind of device it is. Unfortunately the driver only reads the first 8
bits and treats that value as a 32-bit little-endian number, so on a
powerpc the report type seems to be 0x02000000 and is not recognized.

Even on little-endian machines, connecting a media center remote
control (report type 00 01 00 00) with this driver loaded would
presumably fail for the same reason.

Fix both problems by using get_unaligned_le32() to read all four
bytes, which is a little clearer anyway. After this change, the
wireless mouse works on Hugo's PowerBook again.

Based on a patch by Nestor Lopez Casado.
Addresses http://bugs.debian.org/671292

Reported-by: Hugo Osvaldo Barrera <hugo@xxxxxxxxxxxxxxxxxxxxx>
Inspired-by: Nestor Lopez Casado <nlopezcasad@xxxxxxxxxxxx>
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
Signed-off-by: Nestor Lopez Casado <nlopezcasad@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
drivers/hid/hid-logitech-dj.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
index 2b56efc..d44ea58 100644
--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -26,6 +26,7 @@
#include <linux/hid.h>
#include <linux/module.h>
#include <linux/usb.h>
+#include <asm/unaligned.h>
#include "usbhid/usbhid.h"
#include "hid-ids.h"
#include "hid-logitech-dj.h"
@@ -265,8 +266,8 @@ static void logi_dj_recv_add_djhid_device(struct dj_receiver_dev *djrcv_dev,
goto dj_device_allocate_fail;

- dj_dev->reports_supported = le32_to_cpu(
- dj_report->report_params[DEVICE_PAIRED_RF_REPORT_TYPE]);
+ dj_dev->reports_supported = get_unaligned_le32(
+ dj_report->report_params + DEVICE_PAIRED_RF_REPORT_TYPE);
dj_dev->hdev = dj_hiddev;
dj_dev->dj_receiver_dev = djrcv_dev;
dj_dev->device_index = dj_report->device_index;

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