staging: wilc1000: Use crc7 in lib/ rather than a private copy

The code in lib/ is the desired polynomial, and even includes
the 1-bit left shift in the table rather than needing to code
it explicitly.

While I'm in Kconfig, add a description of what a WILC1000 is.
Kconfig questions that require me to look up a data sheet to
find out that I probably don't have one are a pet peeve.

Cc: Adham Abozaeid <adham.abozaeid@microchip.com>
Cc: linux-wireless@vger.kernel.org
Reviewed-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: George Spelvin <lkml@sdf.org>
Link: https://lore.kernel.org/r/20200326152251.19094-1-ajay.kathat@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wilc1000/Kconfig

@@ -2,6 +2,10 @@
 config WILC1000
 	tristate
 	help
+	  Add support for the Atmel WILC1000 802.11 b/g/n SoC.
+	  This provides Wi-FI over an SDIO or SPI interface, and
+	  is usually found in IoT devices.
+
 	  This module only support IEEE 802.11n WiFi.
 
 config WILC1000_SDIO
@@ -22,6 +26,7 @@ config WILC1000_SPI
 	tristate "Atmel WILC1000 SPI (WiFi only)"
 	depends on CFG80211 && INET && SPI
 	select WILC1000
+	select CRC7
 	help
 	  This module adds support for the SPI interface of adapters using
 	  WILC1000 chipset. The Atmel WILC1000 has a Serial Peripheral

drivers/staging/wilc1000/spi.c

@@ -6,6 +6,7 @@
 
 #include <linux/clk.h>
 #include <linux/spi/spi.h>
+#include <linux/crc7.h>
 
 #include "netdev.h"
 #include "cfg80211.h"
@@ -16,64 +17,6 @@ struct wilc_spi {
 
 static const struct wilc_hif_func wilc_hif_spi;
 
-/********************************************
- *
- *      Crc7
- *
- ********************************************/
-
-static const u8 crc7_syndrome_table[256] = {
-	0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f,
-	0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77,
-	0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26,
-	0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e,
-	0x32, 0x3b, 0x20, 0x29, 0x16, 0x1f, 0x04, 0x0d,
-	0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45,
-	0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14,
-	0x63, 0x6a, 0x71, 0x78, 0x47, 0x4e, 0x55, 0x5c,
-	0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b,
-	0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13,
-	0x7d, 0x74, 0x6f, 0x66, 0x59, 0x50, 0x4b, 0x42,
-	0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a,
-	0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69,
-	0x1e, 0x17, 0x0c, 0x05, 0x3a, 0x33, 0x28, 0x21,
-	0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70,
-	0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38,
-	0x41, 0x48, 0x53, 0x5a, 0x65, 0x6c, 0x77, 0x7e,
-	0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36,
-	0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67,
-	0x10, 0x19, 0x02, 0x0b, 0x34, 0x3d, 0x26, 0x2f,
-	0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
-	0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04,
-	0x6a, 0x63, 0x78, 0x71, 0x4e, 0x47, 0x5c, 0x55,
-	0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d,
-	0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a,
-	0x6d, 0x64, 0x7f, 0x76, 0x49, 0x40, 0x5b, 0x52,
-	0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03,
-	0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b,
-	0x17, 0x1e, 0x05, 0x0c, 0x33, 0x3a, 0x21, 0x28,
-	0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60,
-	0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31,
-	0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79
-};
-
-static u8 crc7_byte(u8 crc, u8 data)
-{
-	return crc7_syndrome_table[(crc << 1) ^ data];
-}
-
-static u8 crc7(u8 crc, const u8 *buffer, u32 len)
-{
-	while (len--)
-		crc = crc7_byte(crc, *buffer++);
-	return crc;
-}
-
-static u8 wilc_get_crc7(u8 *buffer, u32 len)
-{
-	return crc7(0x7f, (const u8 *)buffer, len) << 1;
-}
-
 /********************************************
  *
  *      Spi protocol Function
@@ -403,6 +346,11 @@ static int spi_data_write(struct wilc *wilc, u8 *b, u32 sz)
  *      Spi Internal Read/Write Function
  *
  ********************************************/
+static u8 wilc_get_crc7(u8 *buffer, u32 len)
+{
+	return crc7_be(0xfe, buffer, len);
+}
+
 static int wilc_spi_single_read(struct wilc *wilc, u8 cmd, u32 adr, void *b,
 				u8 clockless)
 {