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Subject[PATCH v2 10/20] Staging: ipack: check the device ID space CRC.
Date
From: Jens Taprogge <jens.taprogge@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.taprogge@taprogge.org>
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@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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