>From [EMAIL PROTECTED] Fri Feb 6 15:59:52 2004
>> But as you may know, there is a Linux bug that causes the status to be 0 when
>> sense data (correctly) is available. Libscg _needs_ to add a workarounf for
>> this bug or nothing would work!
>What bug is that? Or rather, under what circumstances is the status equal
>to 0 when it shouldn't be?
Sorry, this is long long ago ---> Check the cdrwite mail archives.
>> It is definitely a severe bug in the kernel to retrieve sense data in case
>> of a DMA size error.
>> - The Linux kernel issues a REQUEST SENSE command ---> this is the first
>> severe bug. It is completely wrong to issue a REQUEST SENSE in
>> case of a DMA Size error.
>> And there exactly is the bug (which is most likely in usb-storage but
>> definitely in the Linux kernel:
>>
>> In case of _only_ a DMA size error, a request sense must not be
>> issued by the driver.
>>
>> If you are the maintainer of this piece of software, please fix this.
>(I'm not the maintainer; Matthew Dharm is.)
>Who says it's wrong to retrieve sense information when there is an
>underrun but not Check Condition? Can you provide a reference to a
>published (or draft) document that states this?
The SCSI standard says that the sense data should retrieved when the
CHECK CONDITION bit is set. ATAPI drives use a bit in the ATA Status
for this purpose.
Read the SCSI CAM standard to see more on this topic.
>Bear in mind that there are some transports which do not provide any
>status at all. The _only_ way for a driver to determine whether an
>error occurred is to get the sense data.
Let us asume such transport does not exist, unless you name at least a
single transport that has no bit that means "CHECK CONDITION".
>In the absence of any official statement to the contrary, the logical
>conclusion is that whether or not the driver gets the sense data is a
>low-level matter. It should only be of interest to the driver and the
>device. Higher-level drivers and user programs should not care one way or
>the other.
If you retrive sense data without reason, you may "read away" a senseful
error status that is related to a different command.
Jörg
--
EMail:[EMAIL PROTECTED] (home) Jörg Schilling D-13353 Berlin
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URL: http://www.fokus.fraunhofer.de/usr/schilling ftp://ftp.berlios.de/pub/schily
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