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    SubjectRe: [PATCH 1/2] Samsung SoC ADC: use regulator (VDD for ADC).
    On Mon, Jun 20, 2011 at 02:16:59PM +0900, MyungJoo Ham wrote:
    > On Sun, Jun 19, 2011 at 12:06 AM, Mark Brown
    > > On Thu, Jun 16, 2011 at 05:30:02PM +0900, MyungJoo Ham wrote:

    > >> +     adc->vdd = regulator_get(dev, S3C_ADC_REGULATOR_NAME);

    > > I'm not convinced that the #define for the name is terribly good style
    > > here, especially given that you actually call it vdd in the code.

    > Then, would it be fine to use as [ regulator_get(dev, "vdd"); ] ?

    Yes.

    > >> +     if (IS_ERR_OR_NULL(adc->vdd)) {
    > >> +             dev_dbg(dev, "operating without regulator %s.\n", S3C_ADC_REGULATOR_NAME);
    > >> +             adc->vdd = NULL; /* Do not control regulator */
    > >> +     }
    > >> +

    > > No, don't do this.  Just unconditionally assume the regulator is present
    > > if power is essential for use of the device.  The regulator API will
    > > stub out correctly if it's not in use to allow things to proceed and if
    > > vdd is genuinely not hooked up then the driver can't function.

    > This ADC driver is for every ADC from S3C24xx series to Exynos4 (and
    > its successors as well).
    > The regulator (VDD for ADC) is essential for the recent chips
    > (S5PC110, S5PV210, and Exynos4).
    > I was just worried about the old boards using the same ADC driver
    > (mach-s3c2410/mach-*.c, mach-s3c6410/mach-*.c, and so on) without
    > ADC-VDD regulators defined.

    If the regulator API is in use on a system it is reasonable to expect it
    to be set up correctly for the system.

    > However, no s3c compliance defconfigs have ever used CONFIG_REGULATOR.
    > Thus, it seems that it's safe to enforce using "vdd" with regulators
    > in plat-samsung's ADC driver.
    > I'll proceed as you have commented.

    Note that SMDK6410 and Cragganmore are both using regulators fairly
    extensively.
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