Re: [PATCH v2] sg: add SG_FLAG_Q_AT_TAIL flag

[Jeremy Linton <jlinton@tributary.com>]

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On 6/5/2014 10:27 AM, Boaz Harrosh wrote:

> 1. aio "scatter_gather" type io. (ie multiple pointers multiple length
> buffers that are written / read from same linear range on device) [The
> async aspect of aio can be implemented via bsg with the write+read system
> calls] 2. mmap of direct device range to user vm memory

	I suspect that belies a bit of a gap in the understanding of the kinds of
applications that use pass-through (vs just using sd, or using it for a guest OS).

	These use cases don't tend to be useful for things like SCSI changers, tape
devices, or SES devices. What is useful is the ability to reset devices, or
maybe some of the other "edge" features provided by SG that never managed to
make it into bsg. Nor are they useful for the monitoring type applications
that use pass-through to pull some vendor specific statistic or device state.

	Furthermore, i've see a fair number of cases where people slap together shell
scripts using the /dev/sg* handles instead of the /dev/bsg/* ones probably
because its simply more convenient.

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