linux-kernel - Re: [PATCH 2/6] usb: xhci-mtk: use __maybe

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Date:	Fri, 4 Mar 2016 17:33:50 +0100
From:	Matthias Brugger <matthias.bgg@...il.com>
To:	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Felipe Balbi <balbi@...nel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb@...r.kernel.org, Mathias Nyman <mathias.nyman@...el.com>,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] usb: xhci-mtk: use __maybe_unused to hide pm
 functions



On 02/03/16 16:24, Arnd Bergmann wrote:
> The mediatek XHCI glue driver uses SET_SYSTEM_SLEEP_PM_OPS() to
> conditionally set the correct suspend/resume options, and
> also puts both the dev_pm_ops and the functions inside of
> an #ifdef testing for CONFIG_PM_SLEEP, but those functions
> then call other code that becomes unused:
>
> drivers/usb/host/xhci-mtk.c:135:12: error: 'xhci_mtk_host_disable' defined but not used [-Werror=unused-function]
> drivers/usb/host/xhci-mtk.c:313:13: error: 'usb_wakeup_enable' defined but not used [-Werror=unused-function]
> drivers/usb/host/xhci-mtk.c:321:13: error: 'usb_wakeup_disable' defined but not used [-Werror=unused-function]
>
> This replaces the #ifdef with __maybe_unused annotations so the
> compiler knows it can silently drop them instead of warning.
>
> For the DEV_PM_OPS definition, we can use an IS_ENABLED() check
> to avoid defining the structure when CONFIG_PM is not set without
> the #ifdef.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---

Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>

>   drivers/usb/host/xhci-mtk.c | 10 +++-------
>   1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> index 9532f5aef71b..79959f17c38c 100644
> --- a/drivers/usb/host/xhci-mtk.c
> +++ b/drivers/usb/host/xhci-mtk.c
> @@ -695,7 +695,6 @@ static int xhci_mtk_remove(struct platform_device *dev)
>   	return 0;
>   }
>
> -#ifdef CONFIG_PM_SLEEP
>   /*
>    * if ip sleep fails, and all clocks are disabled, access register will hang
>    * AHB bus, so stop polling roothubs to avoid regs access on bus suspend.
> @@ -703,7 +702,7 @@ static int xhci_mtk_remove(struct platform_device *dev)
>    * to wake up system immediately after system suspend complete if ip sleep
>    * fails, it is what we wanted.
>    */
> -static int xhci_mtk_suspend(struct device *dev)
> +static int __maybe_unused xhci_mtk_suspend(struct device *dev)
>   {
>   	struct xhci_hcd_mtk *mtk = dev_get_drvdata(dev);
>   	struct usb_hcd *hcd = mtk->hcd;
> @@ -722,7 +721,7 @@ static int xhci_mtk_suspend(struct device *dev)
>   	return 0;
>   }
>
> -static int xhci_mtk_resume(struct device *dev)
> +static int __maybe_unused xhci_mtk_resume(struct device *dev)
>   {
>   	struct xhci_hcd_mtk *mtk = dev_get_drvdata(dev);
>   	struct usb_hcd *hcd = mtk->hcd;
> @@ -744,10 +743,7 @@ static int xhci_mtk_resume(struct device *dev)
>   static const struct dev_pm_ops xhci_mtk_pm_ops = {
>   	SET_SYSTEM_SLEEP_PM_OPS(xhci_mtk_suspend, xhci_mtk_resume)
>   };
> -#define DEV_PM_OPS	(&xhci_mtk_pm_ops)
> -#else
> -#define DEV_PM_OPS	NULL
> -#endif /* CONFIG_PM */
> +#define DEV_PM_OPS IS_ENABLED(CONFIG_PM) ? &xhci_mtk_pm_ops : NULL
>
>   #ifdef CONFIG_OF
>   static const struct of_device_id mtk_xhci_of_match[] = {
>