Re: [PATCH v7] scsi: ufs: add ioctl interface for query request

[ygardi]

> On Wed, Mar 09, 2016 at 07:09:49PM -0000, ygardi@xxxxxxxxxxxxxx wrote:
>> > On Wed, Mar 09, 2016 at 04:11:33PM +0200, Yaniv Gardi wrote:
>> >> This patch exposes the ioctl interface for UFS driver via SCSI device
>> >> ioctl interface. As of now UFS driver would provide the ioctl for
>> query
>> >> interface to connected UFS device.
>> >>
>> >> Reviewed-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
>> >> Signed-off-by: Dolev Raviv <draviv@xxxxxxxxxxxxxx>
>> >> Signed-off-by: Gilad Broner <gbroner@xxxxxxxxxxxxxx>
>> >> Signed-off-by: Yaniv Gardi <ygardi@xxxxxxxxxxxxxx>
>> >
>> > What tool is going to use this ioctl?  Why does userspcae want to do
>> > something "special" with UFS devices?  Shouldn't they just be treated
>> > like any other normal block device?
>> >
>>
>> Any userspace application can be a tool.
>> We already implemented and used a user space application, that sent
>> queries to the UFS devices in order to get information and descriptors.
>
> But do you want to do with that information?  Why does userspace care?
>

i don't really understand the subtext of your question -
as ANY ioctl cb, we decided to implement the ioctl callback of this scsi
device in order to get information like UNIT DESC, DEVICE DESC, FLAGs,
ATTRIBUTES.
When dealing with UFS devices, one should be able to read the
characteristics of the device. why ? well, why not ?
during development of this driver, it was useful in many cases to be able
to communicate with the device, by simple IOCTL command, rather than
implementing ad-hock.

regards,
Yaniv

>> Not only ioctl interface is a useful way to interact with the device,
>> we used it, and found it very helpful in varies cases.
>
> In what case was it helpful?  Why does userspace care about ufs
> specifics, it should just treat it like any other block device and not
> care at all.
>
> thanks,
>
> greg k-h
>