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

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Message-ID: <20190213143646.GC25260@e107981-ln.cambridge.arm.com>
Date:   Wed, 13 Feb 2019 14:36:46 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Kishon Vijay Abraham I <kishon@...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

On Wed, Feb 13, 2019 at 07:08:18PM +0530, Kishon Vijay Abraham I wrote:
> 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.

You mean that every EP controller driver should keep a table of
pci_epc_features (instead of a single instance) to be matched using DT
compatible strings to detect the platform variations ?

Thanks,
Lorenzo