ChangeSet 1.1643.36.7, 2004/03/30 14:26:19-08:00, khali at linux-fr.org [PATCH] I2C: Prevent misdetections in adm1021 driver Yet another patch for the adm1021 chip driver. I refined the detection code a bit in order to prevent chip misdetection. Some chips handled by the adm1021 driver are hard to detect and identify (LM84 and MAX1617) so we tend to accept any chip it the valid I2C address range as one of these. It has caused much, much trouble already. See these threads for example: http://archives.andrew.net.au/lm-sensors/msg04448.html http://archives.andrew.net.au/lm-sensors/msg04624.html http://archives.andrew.net.au/lm-sensors/msg05560.html http://archives.andrew.net.au/lm-sensors/msg05871.html http://archives.andrew.net.au/lm-sensors/msg06754.html http://archives.andrew.net.au/lm-sensors/msg07181.html And this ticket: http://www2.lm-sensors.nu/~lm78/readticket.cgi?ticket=1434 So I thought it would be good to prevent this kind of problems if possible, and read the 8 datasheets again in search for ways to refine the detection method. I changed it in sensors-detect already, and had positive feedback from one user. I will also backport the changes to the driver to the 2.4 version we have in CVS. What the patch does: * Use unused bits of two more registers (configuration and conversion rate) to reduce misdetections. * Return with -ENODEV if the detection fails. * Change the order in which we try to identify the chips. We better finish with the LM84 and the MAX1617, in this order, because they are harder to identify and are more likely to result in false positives. * Refine LM84 detection. The LM84 has less features than the other chips(chip cannot be stopped, conversion rate cannot be set, no low limits) so it has extra unused bits. * Do not intialize the chip if it was detected as an LM84. This one cannot be stopped so why would we try to start it again? And as said right before, conversion rate isn't changeable either. Note that I couldn't test the changes on any supported chip since I don't own any. Still I believe that they should be applied, since the current code already broke one system and seriously harmed several others. I believe it's not critical if it turns out that we reject valid chips (which shouldn't happen if the datasheets are correct, anyway). People will simply let us know and we'll be less restrictive. In the meantime they can force the driver. That said, testers are welcome, as usual. drivers/i2c/chips/adm1021.c | 18 +++++++++++++----- 1 files changed, 13 insertions(+), 5 deletions(-) diff -Nru a/drivers/i2c/chips/adm1021.c b/drivers/i2c/chips/adm1021.c --- a/drivers/i2c/chips/adm1021.c Wed Apr 14 15:14:28 2004 +++ b/drivers/i2c/chips/adm1021.c Wed Apr 14 15:14:28 2004 @@ -246,8 +246,12 @@ /* Now, we do the remaining detection. */ if (kind < 0) { - if ((adm1021_read_value(new_client, ADM1021_REG_STATUS) & 0x03) != 0x00) + if ((adm1021_read_value(new_client, ADM1021_REG_STATUS) & 0x03) != 0x00 + || (adm1021_read_value(new_client, ADM1021_REG_CONFIG_R) & 0x3F) != 0x00 + || (adm1021_read_value(new_client, ADM1021_REG_CONV_RATE_R) & 0xF8) != 0x00) { + err = -ENODEV; goto error1; + } } /* Determine the chip type. */ @@ -265,11 +269,14 @@ else if ((i == 0x4d) && (adm1021_read_value(new_client, ADM1021_REG_DEV_ID) == 0x01)) kind = max1617a; - /* LM84 Mfr ID in a different place */ - else if (adm1021_read_value(new_client, ADM1021_REG_CONV_RATE_R) == 0x00) - kind = lm84; else if (i == 0x54) kind = mc1066; + /* LM84 Mfr ID in a different place, and it has more unused bits */ + else if (adm1021_read_value(new_client, ADM1021_REG_CONV_RATE_R) == 0x00 + && (kind == 0 /* skip extra detection */ + || ((adm1021_read_value(new_client, ADM1021_REG_CONFIG_R) & 0x7F) == 0x00 + && (adm1021_read_value(new_client, ADM1021_REG_STATUS) & 0xAB) == 0x00))) + kind = lm84; else kind = max1617; } @@ -305,7 +312,8 @@ goto error1; /* Initialize the ADM1021 chip */ - adm1021_init_client(new_client); + if (kind != lm84) + adm1021_init_client(new_client); /* Register sysfs hooks */ device_create_file(&new_client->dev, &dev_attr_temp1_max);
