Re: [PATCH] spraid: initial commit of Ramaxel spraid driver

[Yanling Song <songyl@ramaxel.com>]

On Fri, 5 Nov 2021 09:13:55 -0700
Bart Van Assche <bvanassche@acm.org> wrote:

> On 11/5/21 6:02 AM, Yanling Song wrote:
> > We've studied BSG and in general it can work.
> > 
> > The following is our draft design, please give your comments:
> > 1. Applications from user space send commands to driver thru struct
> > sg_io_v4, the private data(used by driver) is saved in
> > sg_io_v4->request and the data length is saved in
> > sg_io_v4->request_len.
> > 
> > 2. SG_IO is used in bsg_ioctl(), the following has to be set because
> > bsg_transport_check_proto() will check the fields:
> >      sg_io_v4->protocol = BSG_PROTOCOL_SCSI;
> >      sg_io_v4->subprotocol = BSG_SUB_PROTOCOL_SCSI_TRANSPORT;
> > 
> > Does the above match the BSG design?  
> 
> I think so. Sample user space code that submits to a BSG interface is
> available e.g. here:
> https://github.com/westerndigitalcorporation/ufs-utils/blob/dev/scsi_bsg_util.c
>
Thanks. We will start coding as the above discussion.
 
> > And one question:
> > The number of queue and queue depth are hardcoded in
> > bsg_setup_queue(). set->nr_hw_queues = 1;
> >         set->queue_depth = 128;
> > 
> > Any reason to do it? how about it does not match the chip's
> > capability? for example, the chip supports 8 hardware queues and
> > each queue depth is 4096?  
> 
> Will BSG commands be processed internally by the spraid driver or
> will these be sent to the hardware queues?
> 
> If there is a need in the spraid driver for concurrent processing of
> BSG commands, feel free to make nr_hw_queues and/or queue_depth
> configurable. I recommend to do this by introducing a new structure
> (bsg_creation_params?) and by passing a pointer to that data
> structure to bsg_setup_queue().
> 
We're not sure if current hardcoded queue and queue depth can meet our
requirement or not now. Will update it later.

> Thanks,
> 
> Bart.