[PATCH v2 10/20] Staging: ipack: check the device ID space CRC.

[Samuel Iglesias Gonsálvez]

From: Jens Taprogge <jens.tapro...@taprogge.org>

We check the CRC and store the result of the check in struct ipac_device.
A warning is emitted if the check fails.  However we leave it to the
IPack module device to refuse to initialize due to a bad CRC.  I have seen
otherwise good modules with bad CRCs.

Signed-off-by: Jens Taprogge <jens.tapro...@taprogge.org>
Signed-off-by: Samuel Iglesias Gonsálvez <sigles...@igalia.com>
---
 drivers/staging/ipack/ipack.c |   59 ++++++++++++++++++++++++++++++++++++++++-
 drivers/staging/ipack/ipack.h |    1 +
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/ipack/ipack.c b/drivers/staging/ipack/ipack.c
index 08b122d..26dc976 100644
--- a/drivers/staging/ipack/ipack.c
+++ b/drivers/staging/ipack/ipack.c
@@ -253,20 +253,71 @@ void ipack_driver_unregister(struct ipack_driver *edrv)
 }
 EXPORT_SYMBOL_GPL(ipack_driver_unregister);
 
+static u16 ipack_crc_byte(u16 crc, u8 c)
+{
+       int i;
+
+       crc ^= c << 8;
+       for (i = 0; i < 8; i++)
+               crc = (crc << 1) ^ ((crc & 0x8000) ? 0x1021 : 0);
+       return crc;
+}
+
+/*
+ * The algorithm in lib/crc-ccitt.c does not seem to apply since it uses the
+ * opposite bit ordering.
+ */
+static u8 ipack_calc_crc1(struct ipack_device *dev)
+{
+       u8 c;
+       u16 crc;
+       unsigned int i;
+
+       crc = 0xffff;
+       for (i = 0; i < dev->id_avail; i++) {
+               c = (i != 11) ? dev->id[i] : 0;
+               crc = ipack_crc_byte(crc, c);
+       }
+       crc = ~crc;
+       return crc & 0xff;
+}
+
+static u16 ipack_calc_crc2(struct ipack_device *dev)
+{
+       u8 c;
+       u16 crc;
+       unsigned int i;
+
+       crc = 0xffff;
+       for (i = 0; i < dev->id_avail; i++) {
+               c = ((i != 0x18) && (i != 0x19)) ? dev->id[i] : 0;
+               crc = ipack_crc_byte(crc, c);
+       }
+       crc = ~crc;
+       return crc;
+}
+
 static void ipack_parse_id1(struct ipack_device *dev)
 {
        u8 *id = dev->id;
+       u8 crc;
 
        dev->id_vendor = id[4];
        dev->id_device = id[5];
        dev->speed_8mhz = 1;
        dev->speed_32mhz = (id[7] == 'H');
+       crc = ipack_calc_crc1(dev);
+       dev->id_crc_correct = (crc == id[11]);
+       if (!dev->id_crc_correct) {
+               dev_warn(&dev->dev, "ID CRC invalid found 0x%x, expected 
0x%x.\n",
+                               id[11], crc);
+       }
 }
 
 static void ipack_parse_id2(struct ipack_device *dev)
 {
        __be16 *id = (__be16 *) dev->id;
-       u16 flags;
+       u16 flags, crc;
 
        dev->id_vendor = ((be16_to_cpu(id[3]) & 0xff) << 16)
                         + be16_to_cpu(id[4]);
@@ -274,6 +325,12 @@ static void ipack_parse_id2(struct ipack_device *dev)
        flags = be16_to_cpu(id[10]);
        dev->speed_8mhz = !!(flags & 2);
        dev->speed_32mhz = !!(flags & 4);
+       crc = ipack_calc_crc2(dev);
+       dev->id_crc_correct = (crc == be16_to_cpu(id[12]));
+       if (!dev->id_crc_correct) {
+               dev_warn(&dev->dev, "ID CRC invalid found 0x%x, expected 
0x%x.\n",
+                               id[11], crc);
+       }
 }
 
 static int ipack_device_read_id(struct ipack_device *dev)
diff --git a/drivers/staging/ipack/ipack.h b/drivers/staging/ipack/ipack.h
index ad4c3bf..77d8075 100644
--- a/drivers/staging/ipack/ipack.h
+++ b/drivers/staging/ipack/ipack.h
@@ -77,6 +77,7 @@ struct ipack_device {
        u32                      id_vendor;
        u32                      id_device;
        u8                       id_format;
+       unsigned int             id_crc_correct:1;
        unsigned int             speed_8mhz:1;
        unsigned int             speed_32mhz:1;
 };
-- 
1.7.10.4

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