Re: [PATCH v4 3/4] fpga: dfl: add basic support DFHv1

[matthew . gerlach]

On Fri, 21 Oct 2022, Ilpo Järvinen wrote:

> On Thu, 20 Oct 2022, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
>
> > From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> >
> > Add generic support for MSI-X interrupts for DFL devices.
> >
> > The location of a feature's registers is explicitly
> > described in DFHv1 and can be relative to the base of the DFHv1
> > or an absolute address.  Parse the location and pass the information
> > to DFL driver.
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > ---
> > v4: s/MSIX/MSI_X
> >     move kernel doc to implementation
> >     use structure assignment
> >     fix decode of absolute address
> >     clean up comment in parse_feature_irqs
> >     remove use of csr_res
> >
> > v3: remove unneeded blank line
> >     use clearer variable name
> >     pass finfo into parse_feature_irqs()
> >     refactor code for better indentation
> >     use switch statement for irq parsing
> >     squash in code parsing register location
> >
> > v2: fix kernel doc
> >     clarify use of DFH_VERSION field
> > ---
>
> > +static int dfh_get_psize(void __iomem *dfh_base, resource_size_t max)
> > +{
> > +	int size = 0;
> > +	u64 v, next;
> > +
> > +	if (!FIELD_GET(DFHv1_CSR_SIZE_GRP_HAS_PARAMS,
> > +		       readq(dfh_base + DFHv1_CSR_SIZE_GRP)))
> > +		return 0;
> > +
> > +	while (size + DFHv1_PARAM_HDR < max) {
> > +		v = readq(dfh_base + DFHv1_PARAM_HDR + size);
> > +
> > +		next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, v);
> > +		if (!(next & ~DFHv1_PARAM_HDR_NEXT_MASK))
>
> In general, try to not use inverse logic for defining masks. However here,
> just change DFHv1_PARAM_HDR_NEXT_OFFSET to not include any extra bits
> (no rsvd nor eop) and you no longer need this extra masking.

I agree that defining the fields better and using FIELD_GET would make 
this code cleaner.

> > +			return -EINVAL;
> > +
> > +		size += next & ~DFHv1_PARAM_HDR_NEXT_MASK;
>
> ...Then you can drop this anding too.
>
> > +
> > +		if (next & DFHv1_PARAM_HDR_NEXT_EOL)
>
> Your docs say EOP, but here you use EOL.

Thanks for catching the inconsistency.

> Change DFHv1_PARAM_HDR_NEXT_EOL such that this is extracted directly from
> v.
>
> --
> i.