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SubjectRe: [rtc-linux] [PATCH 01/02 resend] RTC: Add driver for DS1685 family of real time clocks
On Fri, 12 Dec 2014 17:13:38 -0500 Joshua Kinard <kumba@gentoo.org> wrote:

> From: Joshua Kinard <kumba@gentoo.org>
>
> This adds a driver for the Dallas/Maxim DS1685-family of RTC chips. It
> supports the DS1685/DS1687, DS1688/DS1691, DS1689/DS1693, DS17285/DS17287,
> DS17485/DS17487, and DS17885/DS17887 RTC chips. These chips are commonly found
> in SGI O2 and SGI Octane systems. It was originally derived from a driver
> patch submitted by Matthias Fuchs many years ago for use in EPPC-405-UC
> modules, which also used these RTCs. In addition to the time-keeping
> functions, this RTC also handles the shutdown mechanism of the O2 and Octane
> and acts as a partial NVRAM for the boot PROMS in these systems.
>
> Verified on both an SGI O2 and an SGI Octane.
>
> ...
>
> +static int
> +ds1685_rtc_probe(struct platform_device *pdev)
> +{
> + struct rtc_device *rtc_dev;
> + struct resource *res;
> + struct ds1685_priv *rtc;
> + struct ds1685_rtc_platform_data *pdata;
> + u8 ctrla, ctrlb, hours;
> + unsigned char am_pm;
> + int ret = 0;
> +
> + /* Get the platform data. */
> + pdata = (struct ds1685_rtc_platform_data *) pdev->dev.platform_data;

That cast isn't needed.

> + if (!pdata)
> + return -ENODEV;
> +
> + /* Allocate memory for the rtc device. */
> + rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
> + if (!rtc)
> + return -ENOMEM;
> +
> + /*
> + * Allocate/setup any IORESOURCE_MEM resources, if required. Not all
> + * platforms put the RTC in an easy-access place. Like the SGI Octane,
> + * which attaches the RTC to a "ByteBus", hooked to a SuperIO chip
> + * that sits behind the IOC3 PCI metadevice.
> + */
> + if (pdata->alloc_io_resources) {
> + /* Get the platform resources. */
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -ENXIO;
> + rtc->size = resource_size(res);
> +
> + /* Request a memory region. */
> + /* XXX: mmio-only for now. */
> + if (!devm_request_mem_region(&pdev->dev, res->start, rtc->size,
> + pdev->name))
> + return -EBUSY;
> +
> + /*
> + * Set the base address for the rtc, and ioremap its
> + * registers.
> + */
> + rtc->baseaddr = res->start;
> + rtc->regs = devm_ioremap(&pdev->dev, res->start, rtc->size);
> + if (!rtc->regs)
> + return -ENOMEM;
> + }
> + rtc->alloc_io_resources = pdata->alloc_io_resources;
> +
> + /* Get the register step size. */
> + if (pdata->regstep > 0)
> + rtc->regstep = pdata->regstep;
> + else
> + rtc->regstep = 1;
> +
> + /* Platform read function, else default if mmio setup */
> + if (pdata->plat_read)
> + rtc->read = pdata->plat_read;

I'm trying to understand how this works and I'm not getting very far.
Perhaps it is the intention that some code(?) is to allocate and
populate a ds1685_rtc_platform_data and use platform_device_add_data()
on it, but no such code exists.

Or something. What's going on here?

> + else
> + if (pdata->alloc_io_resources)
> + rtc->read = ds1685_read;
> + else
> + return -ENXIO;
> +
> + /* Platform write function, else default if mmio setup */
> + if (pdata->plat_write)
> + rtc->write = pdata->plat_write;
> + else
> + if (pdata->alloc_io_resources)
> + rtc->write = ds1685_write;
> + else
> + return -ENXIO;
> +
> + /* Platform pre-shutdown function, if defined. */
> + if (pdata->plat_prepare_poweroff)
> + rtc->prepare_poweroff = pdata->plat_prepare_poweroff;
> +
> + /* Platform wake_alarm function, if defined. */
> + if (pdata->plat_wake_alarm)
> + rtc->wake_alarm = pdata->plat_wake_alarm;
> +
> + /* Platform post_ram_clear function, if defined. */
> + if (pdata->plat_post_ram_clear)
> + rtc->post_ram_clear = pdata->plat_post_ram_clear;
> +
> + /* Init the spinlock, workqueue, & set the driver data. */
> + spin_lock_init(&rtc->lock);
> + INIT_WORK(&rtc->work, ds1685_rtc_work_queue);
> + platform_set_drvdata(pdev, rtc);
>
> ...
>


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