* [PATCH 1/2] w1: ds2406: use crc16() instead of crc16_byte() loop
2025-05-13 2:21 [PATCH 0/2] lib/crc16: unexport crc16_table and crc16_byte() Eric Biggers
@ 2025-05-13 2:21 ` Eric Biggers
2025-05-13 7:52 ` Krzysztof Kozlowski
2025-05-13 2:21 ` [PATCH 2/2] lib/crc16: unexport crc16_table and crc16_byte() Eric Biggers
2025-05-13 9:42 ` [PATCH 0/2] " Ard Biesheuvel
2 siblings, 1 reply; 5+ messages in thread
From: Eric Biggers @ 2025-05-13 2:21 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-crypto, Ard Biesheuvel, Krzysztof Kozlowski
From: Eric Biggers <ebiggers@google.com>
Instead of looping through each byte and calling crc16_byte(), instead
just call crc16() on the whole buffer. No functional change.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
drivers/w1/slaves/w1_ds2406.c | 12 ++----------
1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/drivers/w1/slaves/w1_ds2406.c b/drivers/w1/slaves/w1_ds2406.c
index 1cae9b243ff8..76026d615111 100644
--- a/drivers/w1/slaves/w1_ds2406.c
+++ b/drivers/w1/slaves/w1_ds2406.c
@@ -27,12 +27,10 @@ static ssize_t w1_f12_read_state(
const struct bin_attribute *bin_attr,
char *buf, loff_t off, size_t count)
{
u8 w1_buf[6] = {W1_F12_FUNC_READ_STATUS, 7, 0, 0, 0, 0};
struct w1_slave *sl = kobj_to_w1_slave(kobj);
- u16 crc = 0;
- int i;
ssize_t rtnval = 1;
if (off != 0)
return 0;
if (!buf)
@@ -45,13 +43,11 @@ static ssize_t w1_f12_read_state(
return -EIO;
}
w1_write_block(sl->master, w1_buf, 3);
w1_read_block(sl->master, w1_buf+3, 3);
- for (i = 0; i < 6; i++)
- crc = crc16_byte(crc, w1_buf[i]);
- if (crc == 0xb001) /* good read? */
+ if (crc16(0, w1_buf, sizeof(w1_buf)) == 0xb001) /* good read? */
*buf = ((w1_buf[3]>>5)&3)|0x30;
else
rtnval = -EIO;
mutex_unlock(&sl->master->bus_mutex);
@@ -64,12 +60,10 @@ static ssize_t w1_f12_write_output(
const struct bin_attribute *bin_attr,
char *buf, loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
u8 w1_buf[6] = {W1_F12_FUNC_WRITE_STATUS, 7, 0, 0, 0, 0};
- u16 crc = 0;
- int i;
ssize_t rtnval = 1;
if (count != 1 || off != 0)
return -EFAULT;
@@ -81,13 +75,11 @@ static ssize_t w1_f12_write_output(
}
w1_buf[3] = (((*buf)&3)<<5)|0x1F;
w1_write_block(sl->master, w1_buf, 4);
w1_read_block(sl->master, w1_buf+4, 2);
- for (i = 0; i < 6; i++)
- crc = crc16_byte(crc, w1_buf[i]);
- if (crc == 0xb001) /* good read? */
+ if (crc16(0, w1_buf, sizeof(w1_buf)) == 0xb001) /* good read? */
w1_write_8(sl->master, 0xFF);
else
rtnval = -EIO;
mutex_unlock(&sl->master->bus_mutex);
--
2.49.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/2] lib/crc16: unexport crc16_table and crc16_byte()
2025-05-13 2:21 [PATCH 0/2] lib/crc16: unexport crc16_table and crc16_byte() Eric Biggers
2025-05-13 2:21 ` [PATCH 1/2] w1: ds2406: use crc16() instead of crc16_byte() loop Eric Biggers
@ 2025-05-13 2:21 ` Eric Biggers
2025-05-13 9:42 ` [PATCH 0/2] " Ard Biesheuvel
2 siblings, 0 replies; 5+ messages in thread
From: Eric Biggers @ 2025-05-13 2:21 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-crypto, Ard Biesheuvel, Krzysztof Kozlowski
From: Eric Biggers <ebiggers@google.com>
Now that neither crc16_table nor crc16_byte() is used outside
lib/crc16.c, fold them into lib/crc16.c.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
include/linux/crc16.h | 9 +--------
lib/crc16.c | 9 ++++-----
2 files changed, 5 insertions(+), 13 deletions(-)
diff --git a/include/linux/crc16.h b/include/linux/crc16.h
index 9fa74529b317..b861d969b161 100644
--- a/include/linux/crc16.h
+++ b/include/linux/crc16.h
@@ -13,16 +13,9 @@
#ifndef __CRC16_H
#define __CRC16_H
#include <linux/types.h>
-extern u16 const crc16_table[256];
-
-extern u16 crc16(u16 crc, const u8 *buffer, size_t len);
-
-static inline u16 crc16_byte(u16 crc, const u8 data)
-{
- return (crc >> 8) ^ crc16_table[(crc ^ data) & 0xff];
-}
+u16 crc16(u16 crc, const u8 *p, size_t len);
#endif /* __CRC16_H */
diff --git a/lib/crc16.c b/lib/crc16.c
index 5c3a803c01e0..9c71eda9bf4b 100644
--- a/lib/crc16.c
+++ b/lib/crc16.c
@@ -6,11 +6,11 @@
#include <linux/types.h>
#include <linux/module.h>
#include <linux/crc16.h>
/** CRC table for the CRC-16. The poly is 0x8005 (x^16 + x^15 + x^2 + 1) */
-u16 const crc16_table[256] = {
+static const u16 crc16_table[256] = {
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
@@ -40,24 +40,23 @@ u16 const crc16_table[256] = {
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
};
-EXPORT_SYMBOL(crc16_table);
/**
* crc16 - compute the CRC-16 for the data buffer
* @crc: previous CRC value
- * @buffer: data pointer
+ * @p: data pointer
* @len: number of bytes in the buffer
*
* Returns the updated CRC value.
*/
-u16 crc16(u16 crc, u8 const *buffer, size_t len)
+u16 crc16(u16 crc, const u8 *p, size_t len)
{
while (len--)
- crc = crc16_byte(crc, *buffer++);
+ crc = (crc >> 8) ^ crc16_table[(crc & 0xff) ^ *p++];
return crc;
}
EXPORT_SYMBOL(crc16);
MODULE_DESCRIPTION("CRC16 calculations");
--
2.49.0
^ permalink raw reply related [flat|nested] 5+ messages in thread