linux-kernel - Re: [PATCH] rtc: efi: Fail probing if RTC reads don't work

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Date:	Mon, 6 Jun 2016 10:54:48 +0200
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Alexander Graf <agraf@...e.de>
Cc:	rtc-linux@...glegroups.com,
	Leif Lindholm <leif.lindholm@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Alessandro Zummo <a.zummo@...ertech.it>
Subject: Re: [PATCH] rtc: efi: Fail probing if RTC reads don't work

On 5 June 2016 at 11:35, Alexander Graf <agraf@...e.de> wrote:
> While the EFI spec mandates an RTC, not every implementation actually adheres
> to that rule (or can adhere to it - some systems just don't have an RTC).
>
> For those, we really don't want to probe the EFI RTC driver at all, because if
> we do we'd get a non-functional driver that does nothing useful but only spills
> our kernel log with warnings.
>
> Signed-off-by: Alexander Graf <agraf@...e.de>

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

> ---
>  drivers/rtc/rtc-efi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
> index 96d3860..0130afd 100644
> --- a/drivers/rtc/rtc-efi.c
> +++ b/drivers/rtc/rtc-efi.c
> @@ -259,6 +259,12 @@ static const struct rtc_class_ops efi_rtc_ops = {
>  static int __init efi_rtc_probe(struct platform_device *dev)
>  {
>         struct rtc_device *rtc;
> +       efi_time_t eft;
> +       efi_time_cap_t cap;
> +
> +       /* First check if the RTC is usable */
> +       if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
> +               return -ENODEV;
>
>         rtc = devm_rtc_device_register(&dev->dev, "rtc-efi", &efi_rtc_ops,
>                                         THIS_MODULE);
> --
> 1.8.5.6
>