* Re: Help with SATA driver/libata/SCSI subsystem
[not found] <SNT104-W6340D4A4CFCC4D6DEF1140BB610@phx.gbl>
@ 2009-05-13 19:36 ` Jeff Garzik
0 siblings, 0 replies; only message in thread
From: Jeff Garzik @ 2009-05-13 19:36 UTC (permalink / raw)
To: C Z; +Cc: linux-kernel, Linux IDE mailing list
C Z wrote:
> I am attempting to write a SATA driver under libata for a custom core on a Microblaze Xilinx FPGA. I can not get ata_device_add() in drivers/ata/libata-core.c to return successfully.
>
> I have tracked the immediate problem to the function scsi_eh_flush_done_q() in drivers/scsi/scsi_error.c. The problem is this function calls "list_for_each_entry_safe(scmd, next, done_q, eh_entry)". Unfortunately, this returns the result scmd = 0xFFFFFFF0. This very strange address is the result of containerof() being called on a NULL pointer. The NULL pointer is the done_q list head. This is clearly wrong.
>
> I have 2 questions. First, why is libata invoking the error handler after a probe in ata_device_add? This seems very counter intuitive to me. It isn't at all clear why libata needs to do this. Can someone explain the rationale behind this function?
>
> Second, and more importantly, can someone who is experienced with this subsystem explain in simple terms the call flow that happens in the function ata_device_add? I am having trouble understanding which procedure should have issued a command and set up the done_q list head. Therefore I don't know how to track this problem further. Indeed, it doesn't appear to me that anyone actually issues a command during the probe. I'm guessing it was supposed to have been done somewhere, but where/in what function should I start looking? What was the command supposed to have been?
>
> I am using an old kernel version 2.6.20, however I don't believe these subsystems have changed substantially since then.
>
> Any assistance or advice from someone who has dealth with this area of the kernel before is appreciated.
Please cc linux-ide@vger.kernel.org, and turn on word wrapping in your
email.
Please also use an updated kernel, libata has changed substantially
since 2.6.20.
Hardware drivers do not invoke ata_device_add() [which does not exist
anymore], so it sounds like you are doing something really wrong...
Jeff
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