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Date:   Mon, 2 Jan 2023 10:25:00 -0800 (PST)
From:   matthew.gerlach@linux.intel.com
To:     Xu Yilun <yilun.xu@intel.com>
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        basheer.ahmed.muddebihal@intel.com, trix@redhat.com,
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Subject: Re: [PATCH v8 3/4] fpga: dfl: add basic support for DFHv1
In-Reply-To: <Y66uB8/xj+YF4oEr@yilunxu-OptiPlex-7050>
Message-ID: <alpine.DEB.2.22.394.2301021021350.2536944@rhweight-WRK1>
References: <20221228181624.1793433-1-matthew.gerlach@linux.intel.com> <20221228181624.1793433-4-matthew.gerlach@linux.intel.com> <Y66uB8/xj+YF4oEr@yilunxu-OptiPlex-7050>
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On Fri, 30 Dec 2022, Xu Yilun wrote:

> On 2022-12-28 at 10:16:23 -0800, matthew.gerlach@linux.intel.com wrote:
>> From: Matthew Gerlach <matthew.gerlach@linux.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
>> 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.
>>
>> Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
>> Reviewed-by: Ilpo J?rvinen <ilpo.jarvinen@linux.intel.com>
>> ---
>> v8: use struct_size() from overflow.h
>>     add dfh_get_u64_param_vals()
>
> Could you help check my comments?
> https://lore.kernel.org/linux-fpga/alpine.DEB.2.22.394.2212211421210.570436@rhweight-WRK1/T/#md86e3836130ebacd3c088f5c512ba741aac8a4d1


Sorry I missed your earlier comments. I have since responded to them 
specificially.


>
> [...]
>
>>
>> +static u64 *find_param(u64 *params, resource_size_t max, int param_id)
>> +{
>> +	u64 *end = params + max / sizeof(u64);
>> +	u64 v, next;
>> +
>> +	while (params < end) {
>> +		v = *params;
>> +		if (param_id == FIELD_GET(DFHv1_PARAM_HDR_ID, v))
>> +			return params;
>> +
>> +		next = FIELD_GET(DFHv1_PARAM_HDR_NEXT_OFFSET, v);
>> +		params += next;
>> +		if (FIELD_GET(DFHv1_PARAM_HDR_NEXT_EOP, v))
>> +			break;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +/**
>> + * dfh_find_param() - find parameter block for the given parameter id
>> + * @dfl_dev: dfl device
>> + * @param: id of dfl parameter
>> + *
>> + * Return: pointer to start of parameter block, NULL otherwise.
>> + */
>> +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);
>
> Didn't find where to use it?

I understand. Don't export a function unless there is a comsumer for it.

>
>> +
>> +/**
>> + * dfh_get_u64_param_vals() - get array of u64 param values for given parameter id
>
> There is no rule to say one u64 for each property in the parameter block.
> So I don't see the reason for DFL core to provide u64 array for the API,
> And the size of the parameter block is decided by HW, why make the user
> input the value?
>
> As we discussed before, dfl core doesn't try to look into the parameter
> block. So please just provide the const void *data & data_size for drivers.
> This is the most common way to represent a data block.

I will move the parameter parsing helper function to the driver itself.

Thanks for the feedback,
Matthew Gerlach

>
> Thanks,
> Yilun
>
>> + * @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);
>> +
>> +	for (i = 0; i < nvals; i++)
>> +		*pval++ = param[i + 1];
>> +
>> +	return param;
>> +}
>> +EXPORT_SYMBOL_GPL(dfh_get_u64_param_vals);
>> +
>
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