Re: [PATCH v3 07/18] scsi: sd: detect support for command duration limits

Bart Van Assche
2023-01-28T02:52:52Z

On 1/27/23 16:51, Damien Le Moal wrote:
> On 1/27/23 22:00, Hannes Reinecke wrote:
>> Hmm. Calling this during revalidate() makes sense, but how can we ensure
>> that we call revalidate() when the user issues a MODE_SELECT command?
>
> Given that CDLs can be changed with a passthrough command, I do not think we can
> do anything about that, unfortunately. But I think the same is true of many
> things like that. E.g. "let's turn onf/off the write cache without the kernel
> noticing"... But given that on a normal system only privileged applications can
> do passthrough, if that happens, then the system has been hacked or the user is
> shooting himself in the foot.
>
> cdl-tools project (cdladm utility) uses passtrhough but triggers a revalidate
> after changing CDLs to make sure sysfs stays in sync.
>
> As Christoph suggested, we could change all this to an ioctl(GET_CDL) for
> applications... But sysfs is so much simpler in my opinion, not to mention that
> it allows access to the information for any application written in a language
> that does not have ioctl() or an equivalent.
>
> cdl-tools has a test suite all written in bash scripts thanks to the sysfs
> interface :)

My understanding is that combining the sd driver with SCSI pass-through
is not supported and also that there are no plans to support this
combination.

Martin, please correct me if I got this wrong.

Thanks,

Bart.