linux-kernel - Re: [PATCH v4 3/6] libnvdimm, acpi, nfit: Add bus level dsm mask for pass thru.

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Date:   Sat, 1 Jul 2017 13:58:05 -0600
From:   Jerry Hoemann <jerry.hoemann@....com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/6] libnvdimm, acpi, nfit: Add bus level dsm mask for
 pass thru.

On Fri, Jun 30, 2017 at 08:55:22PM -0700, Dan Williams wrote:

...

> On Fri, Jun 30, 2017 at 9:09 AM, Jerry Hoemann <jerry.hoemann@....com> wrote:
> > +               if (cmd == ND_CMD_CALL)
> > +                       dsm_mask = nd_desc->bus_dsm_mask;
> >                 desc = nd_cmd_bus_desc(cmd);
> >                 uuid = to_nfit_uuid(NFIT_DEV_BUS);
> >                 handle = adev->handle;
> > @@ -1613,6 +1615,7 @@ static void acpi_nfit_init_dsms(struct acpi_nfit_desc *acpi_desc)
> >         struct nvdimm_bus_descriptor *nd_desc = &acpi_desc->nd_desc;
> >         const u8 *uuid = to_nfit_uuid(NFIT_DEV_BUS);
> >         struct acpi_device *adev;
> > +       unsigned long dsm_mask;
> >         int i;
> >
> >         nd_desc->cmd_mask = acpi_desc->bus_cmd_force_en;
> > @@ -1624,6 +1627,11 @@ static void acpi_nfit_init_dsms(struct acpi_nfit_desc *acpi_desc)
> >                 if (acpi_check_dsm(adev->handle, uuid, 1, 1ULL << i))
> >                         set_bit(i, &nd_desc->cmd_mask);
> >         set_bit(ND_CMD_CALL, &nd_desc->cmd_mask);
> > +
> > +       dsm_mask = 0x3bf;
> 
> I went ahead and fixed this up to use dsm_mask defined like this:
> 
> +       dsm_mask =
> +               (1 << ND_CMD_ARS_CAP) |
> +               (1 << ND_CMD_ARS_START) |
> +               (1 << ND_CMD_ARS_STATUS) |
> +               (1 << ND_CMD_CLEAR_ERROR) |
> +               (1 << NFIT_CMD_TRANSLATE_SPA) |
> +               (1 << NFIT_CMD_ARS_INJECT_SET) |
> +               (1 << NFIT_CMD_ARS_INJECT_CLEAR) |
> +               (1 << NFIT_CMD_ARS_INJECT_GET);
> 
> This drops function number 0 which userspace has no need to call.

Actually I like to call function 0.  Its an excellent test when
modifying the code path as its a no side effects function whose output
is known in advance and instantly recognizable.  I also use it when
testing new firmware.  

What is the downside to allowing it?  What bad things happen?

Also, I do have to ask why you allow function zero for NVDIMM_FAMILY_MSFT?
-- 

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Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
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