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Subject[PATCH 1/2] w1/w1.c: w1 address crc quick for DS28E04 eeproms
Date
Onewire addresses are 64bit family(8bit), unique_id(48bit), crc(8bit)
(LSBt to MSB) and self-consistent: crc = crc8(family, unique).

DS28E04-100 4096-Bit Addressable 1-Wire EEPROM with PIO have strap pins
to set 7 LSB of the address, unfortunately without updating the crc
part of the address. It is only consistent if all strap pins float high.
[see datasheet 19-6134; Rev 12/11 page 6: 64-bit device id number]

We therefore introduce a special handling of family 0x1c (DS28E04) to
check address consistency with 7 LSBs of the unique_id set to 1.

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Christian Vogel <vogelchr@vogel.cx>
---
drivers/w1/w1.c | 39 +++++++++++++++++++++++++++++++++++++--
1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 15a2ee32f116..f2ae2e563dc5 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -25,6 +25,8 @@
#include "w1_netlink.h"

#define W1_FAMILY_DEFAULT 0
+#define W1_FAMILY_DS28E04 0x1C /* for crc quirk */
+

static int w1_timeout = 10;
module_param_named(timeout, w1_timeout, int, 0);
@@ -913,11 +915,44 @@ void w1_reconnect_slaves(struct w1_family *f, int attach)
mutex_unlock(&w1_mlock);
}

+static int w1_addr_crc_is_valid(struct w1_master *dev, u64 rn)
+{
+ u64 rn_le = cpu_to_le64(rn);
+ struct w1_reg_num *tmp = (struct w1_reg_num *)&rn;
+ u8 crc;
+
+ crc = w1_calc_crc8((u8 *)&rn_le, 7);
+
+ /* quirk:
+ * DS28E04 (1w eeprom) has strapping pins to change
+ * address, but will not update the crc. So normal rules
+ * for consistent w1 addresses are violated. We test
+ * with the 7 LSBs of the address forced high.
+ *
+ * (char*)&rn_le = { family, addr_lsb, ..., addr_msb, crc }.
+ */
+ if (crc != tmp->crc && tmp->family == W1_FAMILY_DS28E04) {
+ u64 corr_le = rn_le;
+
+ ((u8 *)&corr_le)[1] |= 0x7f;
+ crc = w1_calc_crc8((u8 *)&corr_le, 7);
+
+ dev_info(&dev->dev, "DS28E04 crc workaround on %02x.%012llx.%02x\n",
+ tmp->family, (unsigned long long)tmp->id, tmp->crc);
+ }
+
+ if (crc != tmp->crc) {
+ dev_dbg(&dev->dev, "w1 addr crc mismatch: %02x.%012llx.%02x != 0x%02x.\n",
+ tmp->family, (unsigned long long)tmp->id, tmp->crc, crc);
+ return 0;
+ }
+ return 1;
+}
+
void w1_slave_found(struct w1_master *dev, u64 rn)
{
struct w1_slave *sl;
struct w1_reg_num *tmp;
- u64 rn_le = cpu_to_le64(rn);

atomic_inc(&dev->refcnt);

@@ -927,7 +962,7 @@ void w1_slave_found(struct w1_master *dev, u64 rn)
if (sl) {
set_bit(W1_SLAVE_ACTIVE, &sl->flags);
} else {
- if (rn && tmp->crc == w1_calc_crc8((u8 *)&rn_le, 7))
+ if (rn && w1_addr_crc_is_valid(dev, rn))
w1_attach_slave_device(dev, tmp);
}

--
2.30.0
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