linux-kernel - Re: [PATCH 11/15] PCI: pci-epf-test: Use pci_epc_get

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Date:   Wed, 13 Feb 2019 19:08:18 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Alan Douglas <adouglas@...ence.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>,
        Jia-Ju Bai <baijiaju1990@...il.com>,
        <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-rockchip@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 11/15] PCI: pci-epf-test: Use pci_epc_get_features to get
 EPC features

Hi Lorenzo,

On 12/02/19 8:37 PM, Lorenzo Pieralisi wrote:
> On Mon, Jan 07, 2019 at 12:11:44PM +0530, Kishon Vijay Abraham I wrote:
> 
> [...]
> 
>>  static int pci_epf_test_bind(struct pci_epf *epf)
>>  {
>>  	int ret;
>>  	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
>>  	struct pci_epf_header *header = epf->header;
>> +	const struct pci_epc_features *epc_features;
>> +	enum pci_barno test_reg_bar = BAR_0;
>>  	struct pci_epc *epc = epf->epc;
>>  	struct device *dev = &epf->dev;
>> +	bool linkup_notifier = false;
>> +	bool msix_capable = false;
>> +	bool msi_capable = true;
>>  
>>  	if (WARN_ON_ONCE(!epc))
>>  		return -EINVAL;
>>  
>> -	if (epc->features & EPC_FEATURE_NO_LINKUP_NOTIFIER)
>> -		epf_test->linkup_notifier = false;
>> -	else
>> -		epf_test->linkup_notifier = true;
>> -
>> -	epf_test->msix_available = epc->features & EPC_FEATURE_MSIX_AVAILABLE;
>> +	epc_features = pci_epc_get_features(epc, epf->func_no);
> 
> I think it would work out better if struct pci_epc_features was
> allocated in the caller (stack) and pci_epc_get_features() take a
> pointer parameter to it rather than the callee and the callee would just
> have to fill it out, this also removes data in the driver that is not
> really useful.
> 
> Is there any other reason behind the current design choice ?

Some drivers are used by multiple platforms each with different features. In
such cases it's cleaner to have separate epc_feature table for each platform.

I think the driver should maintain some sort of data to even populate
pci_epc_features allocated by EP function driver.

Thanks
Kishon