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Message-ID: <ZVuZOYFzAaCuJjXZ@Asurada-Nvidia>
Date: Mon, 20 Nov 2023 09:36:57 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
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Subject: Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE
On Mon, Nov 20, 2023 at 08:34:58AM +0000, Tian, Kevin wrote:
> > From: Liu, Yi L <yi.l.liu@...el.com>
> > Sent: Monday, November 20, 2023 4:30 PM
> >
> > On 2023/11/20 16:09, Tian, Kevin wrote:
> > >> From: Liu, Yi L <yi.l.liu@...el.com>
> > >> Sent: Friday, November 17, 2023 9:07 PM
> > >> + * @req_len: Length (in bytes) of a request entry in the request array
> > >> + * @req_num: Input the number of cache invalidation requests in the
> > array.
> > >> + * Output the number of requests successfully handled by kernel.
> > >> + * @out_driver_error_code: Report a driver speicifc error code upon
> > failure.
> > >> + * It's optional, driver has a choice to fill it or
> > >> + * not.
> > >
> > > Being optional how does the user tell whether the code is filled or not?
Well, naming it "error_code" indicates zero means no error while
non-zero means something? An error return from this ioctl could
also tell the user space to look up for this driver error code,
if it ever cares.
> > seems like we need a flag for it. otherwise, a reserved special value is
> > required. or is it enough to just document it that this field is available
> > or not per the iommu_hw_info_type?
> >
>
> No guarantee that a reserved special value applies to all vendors.
>
> I'll just remove the optional part. the viommu driver knows what a valid
> code is, if the driver fills it.
Hmm, remove out_driver_error_code? Do you mean by reusing ioctl
error code to tell the user space what driver error code it gets?
Nicolin
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