linux-kernel - Re: [PATCH] resubmit w1_therm:Retries:remove old code add CRC

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Message-ID: <50CFC8F4.60601@avoncliff.com>
Date:	Tue, 18 Dec 2012 01:37:56 +0000
From:	david <david@...ncliff.com>
To:	greg@...ah.com, zbr@...emap.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] resubmit  w1_therm:Retries:remove old code add CRC

w1_therm includes some obsolete code to detect bad_roms, this is no
longer relevant.
The retry code is only used for this bad_rom test, however there is a
CRC check that detects a bad read, but does not trigger a retry. This
patch removes all the bad_rom code and uses the CRC check to trigger
retries.

Signed-off-by: David Stevenson <david@...ncliff.com>

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 92d08e7..5ef583d 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -45,10 +45,6 @@ MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature famil
  static int w1_strong_pullup = 1;
  module_param_named(strong_pullup, w1_strong_pullup, int, 0);
  
-static u8 bad_roms[][9] = {
-				{0xaa, 0x00, 0x4b, 0x46, 0xff, 0xff, 0x0c, 0x10, 0x87},
-				{}
-			};
  
  static ssize_t w1_therm_read(struct device *device,
  	struct device_attribute *attr, char *buf);
@@ -168,16 +164,6 @@ static inline int w1_convert_temp(u8 rom[9], u8 fid)
  	return 0;
  }
  
-static int w1_therm_check_rom(u8 rom[9])
-{
-	int i;
-
-	for (i=0; i<sizeof(bad_roms)/9; ++i)
-		if (!memcmp(bad_roms[i], rom, 9))
-			return 1;
-
-	return 0;
-}
  
  static ssize_t w1_therm_read(struct device *device,
  	struct device_attribute *attr, char *buf)
@@ -194,10 +180,11 @@ static ssize_t w1_therm_read(struct device *device,
  
  	memset(rom, 0, sizeof(rom));
  
-	verdict = 0;
-	crc = 0;
-
  	while (max_trying--) {
+
+		verdict = 0;
+		crc = 0;
+
  		if (!w1_reset_select_slave(sl)) {
  			int count = 0;
  			unsigned int tm = 750;
@@ -249,7 +236,7 @@ static ssize_t w1_therm_read(struct device *device,
  			}
  		}
  
-		if (!w1_therm_check_rom(rom))
+		if (verdict)
  			break;
  	}
  
@@ -260,7 +247,7 @@ static ssize_t w1_therm_read(struct device *device,
  	if (verdict)
  		memcpy(sl->rom, rom, sizeof(sl->rom));
  	else
-		dev_warn(device, "18S20 doesn't respond to CONVERT_TEMP.\n");
+		dev_warn(device, "Read failed CRC check\n");
  
  	for (i = 0; i < 9; ++i)
  		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", sl->rom[i]);
--
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