On Tue, Nov 21, 2023 at 02:50:05AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > Sent: Tuesday, November 21, 2023 1:37 AM > > > > On Mon, Nov 20, 2023 at 08:34:58AM +0000, Tian, Kevin wrote: > > > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > > > Sent: Monday, November 20, 2023 4:30 PM > > > > > > > > On 2023/11/20 16:09, Tian, Kevin wrote: > > > > >> From: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > > > >> 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. > > probably over-thinking but I'm not sure whether zero is guaranteed to > mean no error in all implementations... Well, you are right. Usually HW conveniently raises a flag in a register to indicate something wrong, yet it is probably unsafe to say it definitely. > > > > 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? > > > > No. I just meant to remove the last sentence "It's optional ..." OK. Would it force all IOMMU drivers to report something upon an error/failure? Thanks Nic
