Re: [PATCH v7 3/4] fpga: dfl: add basic support for DFHv1

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On Tue, Dec 20, 2022 at 08:36:51AM -0800, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
> From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> Version 1 of the Device Feature Header (DFH) definition adds
> functionality to the DFL bus.
> A DFHv1 header may have one or more parameter blocks that
> further describes the HW to SW.  Add support to the DFL bus
> to parse the MSI-X parameter.
> The location of a feature's register set 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.


> +/**
> + * dfh_find_param() - find data for the given parameter id
> + * @dfl_dev: dfl device
> + * @param: id of dfl parameter
> + *
> + * Return: pointer to parameter header on success, NULL otherwise.

header is a bit confusing here, does it mean we give and ID and we got
something more than just a data as summary above suggests?

In such case summary and this text should clarify what exactly we get
and layout of the data. Since this is a pointer, who is responsible of
checking out-of-boundary accesses? For instance, if the parameters are
variadic by length the length should be returned as well. Otherwise it
should be specified as a constant somewhere, right?

> + */
> +u64 *dfh_find_param(struct dfl_device *dfl_dev, int param_id)
> +{
> +	return find_param(dfl_dev->params, dfl_dev->param_size, param_id);
> +}
> +EXPORT_SYMBOL_GPL(dfh_find_param);


> +	finfo = kzalloc(sizeof(*finfo) + dfh_psize, GFP_KERNEL);

It sounds like a candidate for struct_size() from overflow.h.
I.o.w. check that header and come up with the best what can
suit your case.

>  	if (!finfo)
>  		return -ENOMEM;

With Best Regards,
Andy Shevchenko

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