On Mon, Sep 14, 2009 at 00:00, James Bottomley <James.Bottomley@xxxxxxx> wrote:
> On Sun, 2009-09-13 at 04:01 +0500, Constantin Baranov wrote:
>> The scsitemp module attaches a device to each SCSI device
>> and registers it in hwmon. Currently the only method of
>> reading temperature is ATA SMART. Adding support of the
>> pure SCSI methods is provided.
>
> The code, as you wrote it looks fine.
>
> The basic problem are the effects. Right at the moment it tries to send
> an ATA_16 encapsulated SMART command to every SCSI device in the system.
> We simply can't allow this. A huge number of SCSI presenting USB
> devices are known to lock up when they see either ATA_X encapsulation or
> SMART commands. It's not really even safe to send ATA_X to SCSI
> devices. The modern ones should all error out fine, but the older ones
> are likely to be less tolerant.
>
> Finally, this:
>
>> + if (attr[2] == 194) {
>> + *temp = attr[7] * 1000;
>> + err = 0;
>> + break;
>
> Smart attribute 194 is highly vendor specific ... for instance my new
> SATA drive doesn't implement it (it does implement 190 instead).
>
> So really, given the complexity of just obtaining the data and the
> problem of matching which data to obtain to which device you have, why
> not just use smartctl from userspace for monitoring? you could even
> just plug into smartd, it seems to have most of the necessary heuristics
> built in already.
There's even a util called hddtemp which handles all this and has a
database of smart attributes to use for most drives.
Thanks,
--
Julian Calaby
Email: julian.calaby@xxxxxxxxx
.Plan: http://sites.google.com/site/juliancalaby/
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