linux-kernel - Re: [PATCH v6 09/18] PCI: dwc: dra7xx: Help compiler to remove unused code

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Date:   Wed, 20 Dec 2017 11:28:55 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Niklas Cassel <niklas.cassel@...s.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     Niklas Cassel <niklass@...s.com>, <linux-omap@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 09/18] PCI: dwc: dra7xx: Help compiler to remove unused
 code



On Wednesday 20 December 2017 04:59 AM, Niklas Cassel wrote:
> The dra7xx driver supports both host and ep mode.
> When enabling support for only one of the modes, help the compiler
> to remove code for the mode that we have not enabled in the driver.
> 
> By adding if (!IS_ENABLED(CONFIG_PCI_DRA7XX_HOST)) return -ENODEV;
> anything after that statement will get silently dropped by the compiler,
> including static functions and structures that are referenced indirectly
> from there.
> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>

Acked-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/pci/dwc/pci-dra7xx.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
> index 07c74ae3614e..224ff8affdce 100644
> --- a/drivers/pci/dwc/pci-dra7xx.c
> +++ b/drivers/pci/dwc/pci-dra7xx.c
> @@ -694,6 +694,11 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  
>  	switch (mode) {
>  	case DW_PCIE_RC_TYPE:
> +		if (!IS_ENABLED(CONFIG_PCI_DRA7XX_HOST)) {
> +			ret = -ENODEV;
> +			goto err_gpio;
> +		}
> +
>  		dra7xx_pcie_writel(dra7xx, PCIECTRL_TI_CONF_DEVICE_TYPE,
>  				   DEVICE_TYPE_RC);
>  		ret = dra7xx_add_pcie_port(dra7xx, pdev);
> @@ -701,6 +706,11 @@ static int __init dra7xx_pcie_probe(struct platform_device *pdev)
>  			goto err_gpio;
>  		break;
>  	case DW_PCIE_EP_TYPE:
> +		if (!IS_ENABLED(CONFIG_PCI_DRA7XX_EP)) {
> +			ret = -ENODEV;
> +			goto err_gpio;
> +		}
> +
>  		dra7xx_pcie_writel(dra7xx, PCIECTRL_TI_CONF_DEVICE_TYPE,
>  				   DEVICE_TYPE_EP);
>  
>