On Tue, 3 Jan 2017, Russell King - ARM Linux wrote:
> On Tue, Jan 03, 2017 at 09:31:18PM +0000, Russell King - ARM Linux wrote: > > On Tue, Jan 03, 2017 at 01:18:29PM -0800, Kees Cook wrote: > > > On Mon, Jan 2, 2017 at 6:06 AM, Russell King - ARM Linux > > > <[email protected]> wrote: > > > > On Mon, Dec 26, 2016 at 05:01:02PM +0530, Bhumika Goyal wrote: > > > >> The object armada38x_rtc_ops of type rtc_class_ops structure is not > > > >> modified after getting initialized by armada38x_rtc_probe. Apart from > > > >> getting referenced in init it is also passed as an argument to the > > > >> function > > > >> devm_rtc_device_register but this argument is of type const struct > > > >> rtc_class_ops *. Therefore add __ro_after_init to its declaration. > > > > > > > > What I'd prefer here is for the structure to be duplicated, with one > > > > copy having the alarm methods and one which does not. Both can then > > > > be made "const" (so placed into the read-only section at link time) > > > > and the probe function select between the two. > > > > > > > > I think that's a cleaner and better solution, even though it's > > > > slightly larger. > > > > > > > > I'm not a fan of __ro_after_init being used where other solutions are > > > > possible. > > > > > > Can the pointer that points to the struct rtc_class_ops be made > > > ro_after_init? > > > > It's passed into the RTC core code, and probably stored in some dynamically > > allocated object, so probably no. It's the same class of problem as every > > file_operations pointer in the kernel, or the thousand other operations > > structure pointers that a running kernel has. I'm not sure to understand the question and the response. A quick check with grep suggests that most rtc_class_ops pointers are already const. There seem to be just some instances in specific drivers that are not. julia > > For the elimination of doubt, this is what I meant in my original email. > As you can see, there's nothing to be marked as __ro_after_init anymore. > > drivers/rtc/rtc-armada38x.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/drivers/rtc/rtc-armada38x.c b/drivers/rtc/rtc-armada38x.c > index 9a3f2a6f512e..a4166ccfce36 100644 > --- a/drivers/rtc/rtc-armada38x.c > +++ b/drivers/rtc/rtc-armada38x.c > @@ -202,7 +202,7 @@ static irqreturn_t armada38x_rtc_alarm_irq(int irq, void > *data) > return IRQ_HANDLED; > } > > -static struct rtc_class_ops armada38x_rtc_ops = { > +static const struct rtc_class_ops armada38x_rtc_ops = { > .read_time = armada38x_rtc_read_time, > .set_time = armada38x_rtc_set_time, > .read_alarm = armada38x_rtc_read_alarm, > @@ -210,8 +210,15 @@ static struct rtc_class_ops armada38x_rtc_ops = { > .alarm_irq_enable = armada38x_rtc_alarm_irq_enable, > }; > > +static const struct rtc_class_ops armada38x_rtc_ops_noirq = { > + .read_time = armada38x_rtc_read_time, > + .set_time = armada38x_rtc_set_time, > + .read_alarm = armada38x_rtc_read_alarm, > +}; > + > static __init int armada38x_rtc_probe(struct platform_device *pdev) > { > + const struct rtc_class_ops *ops; > struct resource *res; > struct armada38x_rtc *rtc; > int ret; > @@ -242,19 +249,22 @@ static __init int armada38x_rtc_probe(struct > platform_device *pdev) > 0, pdev->name, rtc) < 0) { > dev_warn(&pdev->dev, "Interrupt not available.\n"); > rtc->irq = -1; > + } > + platform_set_drvdata(pdev, rtc); > + > + if (rtc->irq != -1) { > + device_init_wakeup(&pdev->dev, 1); > + ops = &armada38x_rtc_ops; > + } else { > /* > * If there is no interrupt available then we can't > * use the alarm > */ > - armada38x_rtc_ops.set_alarm = NULL; > - armada38x_rtc_ops.alarm_irq_enable = NULL; > + ops = &armada38x_rtc_ops_noirq; > } > - platform_set_drvdata(pdev, rtc); > - if (rtc->irq != -1) > - device_init_wakeup(&pdev->dev, 1); > > rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, pdev->name, > - &armada38x_rtc_ops, THIS_MODULE); > + ops, THIS_MODULE); > if (IS_ERR(rtc->rtc_dev)) { > ret = PTR_ERR(rtc->rtc_dev); > dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret); > > -- > RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ > FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up > according to speedtest.net. >
