linux-kernel - Re: [PATCH v8 3/4] fpga: dfl: add basic support for DFHv1

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Message-ID: <alpine.DEB.2.22.394.2212290911001.1857691@rhweight-WRK1>
Date:   Thu, 29 Dec 2022 09:31:02 -0800 (PST)
From:   matthew.gerlach@...ux.intel.com
To:     Andy Shevchenko <andriy.shevchenko@...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, linux-kernel@...r.kernel.org,
        tianfei.zhang@...el.com, corbet@....net,
        gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        jirislaby@...nel.org, geert+renesas@...der.be,
        niklas.soderlund+renesas@...natech.se, macro@...am.me.uk,
        johan@...nel.org, lukas@...ner.de, ilpo.jarvinen@...ux.intel.com,
        marpagan@...hat.com, bagasdotme@...il.com
Subject: Re: [PATCH v8 3/4] fpga: dfl: add basic support for DFHv1



On Thu, 29 Dec 2022, Andy Shevchenko wrote:

> On Wed, Dec 28, 2022 at 10:16:23AM -0800, matthew.gerlach@...ux.intel.com wrote:
>> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>>
>> 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
>
> Single space is enough.

Yes, single space is enough. Two spaces after a period is hard habit for 
me break. I will update in v9.

>
>> 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.
>
> I'm wondering what DFL states for.

I will define DFL in the commit message like DFH in the next revision.

>
> ...
>
>> +/**
>> + * dfh_get_u64_param_vals() - get array of u64 param values for given parameter id
>> + * @dfl_dev: dfl device
>> + * @param: id of dfl parameter
>> + * @pval: location of parameter data destination
>> + * @nvals: number of u64 elements of parameter data
>> + *
>> + * Return: pointer to start of parameter block, PTR_ERR otherwise
>> + */
>> +u64 *dfh_get_u64_param_vals(struct dfl_device *dfl_dev, int param_id, u64 *pval, int nvals)
>> +{
>> +	u64 *param = find_param(dfl_dev->params, dfl_dev->param_size, param_id);
>> +	u64 next;
>> +	int i;
>> +
>> +	if (!param)
>> +		return ERR_PTR(-ENOENT);
>> +
>> +	next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, *param);
>> +
>> +	if (nvals >= next)
>> +		return ERR_PTR(-ENOMEM);
>
> ENODATA ?

ENODATA does seem to be more accurate than ENOMEM in this case.

>
>> +	for (i = 0; i < nvals; i++)
>> +		*pval++ = param[i + 1];
>
> memcpy() ?

Using memcpy() will make code cleaner.

>
>> +	return param;
>> +}
>
> ...
>
>> +	finfo = kzalloc(struct_size(finfo, params, dfh_psize/sizeof(u64)), GFP_KERNEL);
>
> ' / ' (mind the spaces)

Yes, I will mind the spaces.

>
> Also, perhaps better to use sizeof(*params) or what is the member of that
> structure. So it will be more robust against possible changes.

params is the name of the structure member that is the trailing array.

>
>>  	if (!finfo)
>>  		return -ENOMEM;
>
> -- 
> With Best Regards,
> Andy Shevchenko

Thanks for the feedback,
Matthew Gerlach

>
>
>