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

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Date:   Fri, 21 Oct 2022 12:07:52 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Matthew Gerlach <matthew.gerlach@...ux.intel.com>
cc:     hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com,
        basheer.ahmed.muddebihal@...el.com, trix@...hat.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        tianfei.zhang@...el.com, corbet@....net,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        Jiri Slaby <jirislaby@...nel.org>, geert+renesas@...der.be,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        niklas.soderlund+renesas@...natech.se, macro@...am.me.uk,
        johan@...nel.org, Lukas Wunner <lukas@...ner.de>,
        marpagan@...hat.com
Subject: Re: [PATCH v4 3/4] fpga: dfl: add basic support DFHv1

On Thu, 20 Oct 2022, matthew.gerlach@...ux.intel.com wrote:

> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> 
> 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@...ux.intel.com>
> ---

> @@ -934,56 +962,108 @@ static u16 feature_id(u64 value)
>  	return 0;
>  }
>  
> +static void *find_param(void *base, resource_size_t max, int param)
> +{
> +	int off = 0;
> +	u64 v, next;
> +
> +	while (off < max) {
> +		v = *(u64 *)(base + off);
> +		if (param == FIELD_GET(DFHv1_PARAM_HDR_ID, v))
> +			return base + off + DFHv1_PARAM_DATA;
> +
> +		next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, v);
> +		off += next & ~DFHv1_PARAM_HDR_NEXT_MASK;
> +		if (next & DFHv1_PARAM_HDR_NEXT_EOL)
> +			break;
> +
> +	}
> +
> +	return NULL;
> +}
> +
> +/**
> + * dfh_find_param() - find data for the given parameter id
> + * @dfl_dev: dfl device
> + * @param: id of dfl parameter
> + *
> + * Return: pointer to parameter data on success, NULL otherwise.
> + */
> +void *dfh_find_param(struct dfl_device *dfl_dev, int param)
> +{
> +	return find_param(dfl_dev->params, dfl_dev->param_size, param);
> +}
> +EXPORT_SYMBOL_GPL(dfh_find_param);

Do you expect this split between dfh_find_param() and find_param() to
be useful in the future? If no other callers are expected, I'd just pull 
find_param() into dfh_find_param() and create local variables for base and 
max.

-- 
 i.