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    SubjectRe: [PATCH] drivers, char: add U-Boot bootcount driver
    On Sun, Dec 04, 2011 at 10:45:21AM +0100, Heiko Schocher wrote:
    > This driver implements the Linux kernel half of the boot count feature -
    > the boot counter can only be reset after it is clear that the
    > application has been started and is running correctly, which usually
    > can only be determined by the application code itself. Thus the reset
    > of the boot counter must be done by application code, which thus needs
    > an appropriate driver.

    An appropriate mechanism, not necessarily a driver, see below.

    > Required feature by the Carrier Grade Linux Requirements Definition;
    > see for example document "Carrier Grade Linux Requirements Definition
    > Overview V3.0" at
    >
    > http://www.linuxfoundation.org/collaborate/workgroups/cgl/requirements#SMM.6.0_Boot_Cycle_Detection
    >
    > Description: OSDL CGL specifies that carrier grade Linux
    > shall provide support for detecting a repeating reboot cycle
    > due to recurring failures. This detection should happen in
    > user space before system services are started.

    So, technically, a flag would be enough, not necessarily a counter? Although a
    counter probably has more advantages...

    > This driver provides read/write access to the U-Boot bootcounter
    > through PROC FS and/or sysFS file.

    Why ProcFS? Why ProcFS and/or SysFS? Which has priority? Why not /dev?

    > The bootcountregister gets configured via DTS.
    > for example on the enbw_cmc board:
    >
    > bootcount@0x23060 {
    > compatible = "uboot,bootcount";

    No. I assume you are not the vendor of what is at 0x23060, the actual device.
    Only the device must be encoded in the compatible-entry which then implies the
    bootcount functionality. Also, keep in mind that your solution should be
    generic for bootloaders.

    > reg = <0x23060 0x20>;

    I assume that non-volatile memory would qualify as a boot-counter, so those
    could be tied to I2C busses etc? reg would not fit then.

    I do wonder if it makes more sense to add such functionality to the
    watchdog-core to save the additional device (CCed). Needs a second thought,
    though...

    Regards,

    Wolfram

    --
    Pengutronix e.K. | Wolfram Sang |
    Industrial Linux Solutions | http://www.pengutronix.de/ |
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